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The Cygnus Dual Beam Radiographic Facility consists of two identical radiographic sources each with a dose rating of ∼4-rad at 1 m, and a ∼1-mm diameter spot size. The development of the rod pinch diode (RPD) was responsible for the ability to meet these criteria. The RPD in each machine uses a 0.75-mm tungsten diameter tapered anode rod extended through a 9-mm diameter cathode aperture. When properly configured, the electron beam born off the aperture edge can self-insulate and pinch onto the tip of the rod creating an intense, small x-ray source. These sources are utilized in concert with an imaging system on complex experiments, which are single-shot, high-value events. In such an application there is an emphasis on machine performance (reliability and reproducibility). Vacuum quality is a significant determinator for source performance. In this paper we discuss the Cygnus Dual Beam Radiographic Facility, the associated vacuum systems, vacuum monitor calibration and a multi-purpose vacuum chamber. Vacuum system performance, using various enhancements, will be reported. Using the vacuum system enhancements, as well as other machine tweaks, recent source performance has improved. This new level of performance will be presented via dosimetry and electrical measurements.

This paper contains a study of the motion of a rotor possessing unequal flexibilities in two mutually perpendicular directions and mounted in bearings which likewise possess different stiffnesses in two mutually perpendicular directions, say, the horizontal and vertical directions. A two-pole turbogenerator is an example of such a rotor. As known, the effect of ρ, the fractional inequality in rotor flexibilities, by itself, that is, without unequal bearing flexibilities, consists in giving rise to an unstable range of speed near the critical whose width depends upon ρ; the larger ρ is, the wider is the unstable range. If neither ρ nor σ vanishes (σ = fractional inequality of bearing flexibilities), the investigation becomes more difficult due to the fact that the principal flexibility directions are fixed for the bearings but rotate for the rotor. The differential equations of motion now acquire periodic coefficients whose period is half the rotation period. Their solution shows that near the main critical speed, for small ρ the unstable range splits up into three parts, which coalesce into one range for large ρ. The separation of three unstable ranges increases with σ. A further slight instability also occurs when the rotor speed is near half of the main critical speed. If one attempts to revolve such a rotor at a constant speed inside an unstable range, it may, even if in perfect balance, whirl with an exponentially increasing amplitude. With friction the amount of instability decreases and the size of the unstable regions decreases too, and with sufficient friction complete stability is restored. The friction necessary to restore stability is computed and the effect of unbalance on the steady-state amplitudes is studied. The solution of linear differential equations with periodic coefficients leads to an infinite number of algebraic linear equations in an infinite number of coefficients. Various ways of solving these equations and of speeding up the convergence of the solution are discussed in detail.

Gain-cell embedded DRAM (GC-eDRAM) is an attractive alternative to traditional SRAM, due to its high-density, low-leakage, and inherent 2-ported operation, yet, its dynamic nature leads to limited retention time that requires periodic, power-hungry refresh cycles. This drawback is further aggravated in scaled technologies, where increased leakage currents and decreased in-cell storage capacitances lead to accelerated data integrity deterioration. However, the emerging approximate computing paradigm utilizes the inherent error resilience of some applications to tolerate data errors. Such error tolerance can be exploited by reducing the refresh rate in GC-eDRAM to achieve a substantial decrease in power consumption, at the cost of an increase in cell failure probability. In this paper, we present the first fabricated and fully functional GC-eDRAM in a 28 nm bulk CMOS technology. The array, which is based on a novel mixed-V t 4T bitcell, can be used in both traditional and for approximate computing applications, featuring a small silicon footprint and supporting high-performance operation. Silicon measurements demonstrate successful operation at 800 Mhz under a 900 mV supply, while retaining almost 30% lower area than a single-ported 6T SRAM in the same technology.

Ensuring long processor lifetimes by limiting failuresdue to wear-out related hard errors is a critical requirementfor all microprocessor manufacturers. We observethat continuous device scaling and increasing temperaturesare making lifetime reliability targets even harder to meet.However, current methodologies for qualifying lifetime reliabilityare overly conservative since they assume worst-caseoperating conditions. This paper makes the case thatthe continued use of such methodologies will significantlyand unnecessarily constrain performance. Instead, lifetimereliability awareness at the microarchitectural design stagecan mitigate this problem, by designing processors that dynamicallyadapt in response to the observed usage to meeta reliability target.We make two specific contributions. First, we describean architecture-level model and its implementation, calledRAMP, that can dynamically track lifetime reliability, respondingto changes in application behavior. RAMP isbased on state-of-the-art device models for different wear-outmechanisms. Second, we propose dynamic reliabilitymanagement (DRM) - a technique where the processorcan respond to changing application behavior to maintainits lifetime reliability target. In contrast to currentworst-case behavior based reliability qualification methodologies,DRM allows processors to be qualified for reliabilityat lower (but more likely) operating points than theworst case. Using RAMP, we show that this can save costand/or improve performance, that dynamic voltage scalingis an effective response technique for DRM, and that dynamicthermal management neither subsumes nor is sub-sumedby DRM.

BackgroundRecent advances in mobile technologies have created new opportunities to reach broadly into populations that are vulnerable to health disparities. However, mobile health (mHealth) strategies could paradoxically increase health disparities, if low socioeconomic status individuals lack the technical or literacy skills needed to navigate mHealth programs. ObjectiveThe aim of this study was to determine whether patients from vulnerable populations could successfully navigate and complete an mHealth patient decision aid. MethodsWe analyzed usability data from a randomized controlled trial of an iPad program designed to promote colorectal cancer (CRC) screening. The trial was conducted in six primary care practices and enrolled 450 patients, aged 50-74 years, who were due for CRC screening. The iPad program included a self-survey and randomly displayed either a screening decision aid or a video about diet and exercise. We measured participant ability to complete the program without assistance and participant-rated program usability. ResultsTwo-thirds of the participants (305/450) were members of a vulnerable population (limited health literacy, annual income < US $20,000, or black race). Over 92% (417/450) of the participants rated the program highly on all three usability items (90.8% for vulnerable participants vs 96.6% for nonvulnerable participants, P=.006). Only 6.9% (31/450) of the participants needed some assistance to complete the program. In multivariable logistic regression, being a member of a vulnerable population was not associated with needing assistance. Only older age, less use of text messaging (short message service, SMS), and lack of Internet use predicted needing assistance. ConclusionsIndividuals who are vulnerable to health disparities can successfully use well-designed mHealth programs. Future research should investigate whether mHealth interventions can reduce health disparities.

It is well known that when wood and other vegetable substances are submitted to destructive distillation, there is produced, among other matters, a black dense fluid resembling molasses or common tar. My connection’ with the Ordnance powder-mills having compelled me to examine some of the properties of this substance, which is obtained in large quantities in the process of making charcoal, I was induced to extend my enquiries, in consequence of finding that the nature of the compound has not hitherto been understood. As it is commonly called tar by the workmen, I shall use this term for want of a better. This tar is very inflammable, and so liquid that it may be burnt in a lamp. Although it appears to be an uniform fluid, it contains a great quantity of acetic acid, in a state of loose combination or mixture. For, by washing with water, a great part of this is separated; the water at the same time acquiring a colour from a portion of the tar which is retained in solution by the acid. Boiling water takes up a larger portion, and the tar acquires from this operation a thicker and more pitchy consistence. Lime and the carbonated alkalies separate the acid with ease, carrying away also a portion of the tar which continues united to the solution. With subcarbonate of potash it thus forms in the first instance an uniform solution of a brown colour, but a continuance of trituration or boiling renders it pitchy and

Sir, Since you did me the honour of submitting to the Royal Society my experiments on the comparative light of the Cassegrainian and Gregorian telescopes, I have been so fortunate as to have an opportunity of establishing the conclusions deduced from them by another experiment, the detail of which I trust will not prove unacceptable. The telescopes used on the present occasion were the excellent Gregorian described in my former paper, and a new Cassegrainian constructed by Mr. Crickmore. The diameter of the large speculum of this instrument is 4, 9 inches, the distance between the mirrors only 18 inches, and it bears a power of about 550 (as roughly determined by experiment) with perfect distinctness and considerable light.

Dear Sir, In prosecuting the experiments on the depolarisation of light, which you lately did me the honour to lay before the Royal Society, I have been led to the discovery of a remarkable pro­perty of soft transparent solids, in virtue of which they ex­hibit, by simple pressure, all the optical qualities of doubly polarising crystals. In the paper on depolarisation to which I have now alluded, it has been shown that a mixture of bees' wax and rosin, when melted and cooled between two plates of glass, depolarises a ray which falls upon it at a vertical inci­dence, w'hile the same substance, pressed between two plates of glass, without the aid of heat, produces no effect when the polarised ray falls perpendicularly upon it, but depolarises it at an oblique incidence. In this experiment the crystallization was not produced by pressure, as the unmelted bees' wax was already crystallized; but it is obvious, either that the pressure had modified the natural crystallization of the bees' wax, so as to enable it to depolarise only at an oblique inci­dence, or that its liquefaction between two plates of glass had produced such a change, as to communicate to it the property of perpendicular depolarisation. In whatever manner this difference of action was produced, the effects of pressure seemed to require farther investigation, and in order to be able to apply a sufficient force, without injuring the structure of the substance, I employed animal jellies which could be brought to any degree of tenacity with­out losing their transparency.

Modern accelerator driven experiments like linear colliders or spallation sources are supplied by RF amplifiers using klystrons. The cathode voltage for these klystrons can be generated by long pulse modulators generating highly accurate voltage pulses in the length of milliseconds. Conventional designs using pulse transformers become huge for long pulses. The series-parallel resonant converter (SPRC) topology avoids this drawback as the transformer is operating at high frequencies. This paper presents a comprehensive design approach for SPRC modules, which is based on an optimization procedure containing an electrical model of the resonant circuit and a thermal model of the semiconductors. In addition, an insulation and a leakage design procedure and a thermal model of the transformer are also presented. Finally, this procedure provides the optimal design parameters of the resonant circuit elements. With these parameters, a global optimizer chooses the optimum amount of modules connected in series and/or in parallel to fulfill the given restrictions. The efficiency of a basic SPRC-module is 94.7% with a pulsed power density of 4.63 kW/l.

The provision of legal aid to date is still not fully felt for the poor, especially the legal and justice aspects. The issuance of Law Number 16 Year 2011 on Legal Aid or so-called UUBH becomes an important breakthrough in constitutional development post-reformasi law. This paper focuses on the provision of legal aid by the Legal Aid Post (Posbakum) in the Religious Court of Bengkulu City. This research is a qualitative research with interview to get data. The results showed that the implementation of legal services through Posbakum in Religious Courts of Bengkulu City has been going well. Although in the implementation of legal services is still constrained by the human resources (HR) in Posbakum, but if dihat from the administrative process and the impact of legal aid services, the overall implementation of legal services through Posbakum in the Court of Religion has been running well according to achievements based on legislation

In the Philosophical Transactions for 1825, I gave an account of a floating collimator, and added a suggestion for the construction of a vertical floating collimator which had not then been carried into effect. I have since had an instrument of that description made, with such improvements as occasion required, and the results which it has afforded have been so satisfactory that I am induced to lay them before the Society. The collimator which formed the subject of the paper I have mentioned was a horizontal floating collimator. This, in the manner in which I then used it, was the worst form in which the instrument could have been employed; as it was necessary to take the float out of the mercury and replace it in order to complete each observation. The result was therefore liable to be vitiated by any particle of dust or minute bubble of air which might have found a place between the float and the mercury. It cannot therefore but be considered as surprising, that out of one hundred and fifty-one results, only twenty-eight were found in error to an amount exceeding one second, the greatest error being 2".58 and the next 2".

In a paper I had the honour to present to the Royal Society in January last, relative to the construction of achromatic telescopes with fluid lenses, I have stated that between the temperatures of 31° and 84° I had not been able to detect any very sensible change in the index denoting the focal length of the telescope: these observations however being made at intervals of some months, I was doubtful whether there might not be some minute variation which had escaped my notice; and I have since, by means of temperature artificially produced, ascertained that there is a certain small change, and the amount of that change, which is 154/1000ths of an inch in the length of the telescope employed, between each of these extremes and the mean temperature of 57°. That is, the eye-piece of the telescope and the fluid lens being fixed, as was the case in this instrument, the plate lens required an adjustment of 0.134 of an inch, between the temperature of 57° and each of the above extremes, to produce the brightest and most perfect image. Before I proceed, however, to detail the results of my inquiry on these subjects, it will be proper to define a few terms which appear in one or two instances to have been misunderstood.

The same views which the author originally had of the periscopic construction of spectacles, naturally suggested to him a corresponding improvement in the camera obscura. But though it is evident that enlargement of the field of view, and some improvement in the distinctness of images obliquely situated, might be made by causing each part of a lens to be as nearly as may be at right angles to each pencil of rays that are to be collected to a focus, it was not clear to what extent this principle could be carried where the portion of lens is necessarily large, and consequently includes parts that may require a different form for preserving distinctness of other pencils of rays. He has, accordingly, made trial of different forms of meniscus for this purpose, and describes the construction which appears to possess the greatest advantage with least detriment to the brilliancy and distinctness of objects centrally situated. The radii of curvature here preferred are in the proportion of 2 to 1.

The experiments detailed in the present letter were conducted exactly in the same manner as those detailed by Capt. Kater in his former communication, for the purpose of comparing a new Casse­grainian telescope, made by Mr. Crickmore of Ipswich, with the Gregorian used in the former experiments. The diameter of the large speculum in this instrument is 4.9 inches, but was reduced by a ring of pasteboard to 3.6, in order to render the illumination equal to that of the Gregorian, in which the large speculum measured 3.95 inches. The areas exposed to the light being estimated at 7.152 and 10.593, and the magnifying powers at the same time being 157 and 125 respectively, the illuminating powers of the two telescopes are inferred to be as 678 to 290.

When steam is passed through a tube surrounded with water, it is well known that it becomes condensed on the sides of the tube so long as the water continues at a lower temperature than that of the steam; but since the latent heat given out in the condensation of steam soon raises the temperature of the water to 212°, all transfer of heat ceases at that temperature, and the steam then passes un-condensed. But since the temperature at which water may be raised into vapour depends on the pressure of the atmosphere, the temperature of the surrounding water may be kept permanently lower, by removing that pressure, so as permanently to act in condensing the vapour of the first distillation; and being itself raised into vapour by mere transfer of the same original quantity of heat, may be received as an additional product of the same process, by a suitable arrangement of the apparatus. For this purpose, the vessel which serves as condensing worm-tub to the first distillation requires to be fitted with a head and a receiver, all perfectly air-tight; and it may with most convenience be so constructed, that, by application of heat in the first instance to this vessel, the water within may be made to boil completely, so that the air within it will be thereby expelled, and, by a valve or cock, may be prevented from returning when the heat is withdrawn.

On the evening of the 24th of December last, Mr. Howard found the barometer at his house at Tottenham Green at 28·20 inches. The wind was moderate at S. E., the temperature 45°, and water boiled freely at 210°. At 11 p. m. the barometer fell to 27·96 inches, and at 5 a. m. on the 25th to 27·82, below which the author thinks it did not descend. By 8 a. m. it again reached 28. In the twenty-four hours preceding, 0·8 inch rain had fallen, but in the twenty-four hours following there fell none, nor was the wind strong. By midnight on the 25th the quicksilver reached 28·07 inches, and remained there during the twelve hours following,—a thing very rare in our climate. The quicksilver then rose in an uninterrupted curve, and on the 31st touched upon 30 inches, with fine weather. A diagram showing the state of the barometer during the last two months of 1821, as well as the quarter of the wind and quantity of rain fallen, accompanies this paper. During these two months the rain amounted to 10·10 inches, a quantity without precedent in the same space of time at London.

Mr. Ritchie, after a brief exposition of the theoretical views which led him to the construction of his photometer, lays down the fol­lowing as the principles on which it depends:— 1. That radiant heat does not permeate glass. 2. That light is capable of combining with substances which stop it, and expanding them as heat does. 3. That the intensity of light is in the inverse ratio of the squares of the distance.

The apparatus described in this paper (of which a drawing is now laid on the table) is intended to determine the situation of the line of collimation of a telescope attached to an astronomical circle, with respect to the zenith or horizon in some one position of the instru­ment; in other words, to determine the zero point of the divisions on the limb. This is at present usually performed by the use of the level or the plumb line, or by the reflection of an object from the surface of a fluid. The author describes the defects and inconveniencies of each of these methods. Those of the plumb line, when applied to small instruments (to the improvement of which he describes his at­tention to have been particularly directed,) are referrible chiefly to want of sufficient delicacy. Those of the level are referrible to a va­riety of causes not under the command of the observer; while ob­servations, by reflection, the most perfect perhaps of any now prac­tised, require an union of favourable circumstances rarely occurring. Add to these when levels or plumb lines are used, the necessity of reversing the instrument, and observing out of the meridian. And when observations are made by reflection, that of deferring the corresponding observation to the following night, which has proved so great an inconvenience at Greenwich, as to necessitate the erection of a second circle for the purpose of simultaneous observation. The principles on which the floating collimator is constructed are two: the first is the property of a telescope employed by Mr. Gauss, and subsequently by Mr. Bessel, in virtue of which the cross wires of a telescope adjusted to distinct vision on the stars, may be distinctly seen by another telescope, also so adjusted, at whatever distance the telescopes may be placed, provided their axes coincide; the rays diverging from the cross wires of either telescope, emerging parallel from its object-glass, and being therefore refracted by that of the other telescope to its sidereal focus, as if they came from an infinite distance. The author here translates an account by Professor Bessel, of a method of using this principle to determine the horizontal or zenith point of a circle by the use of a level, employed to place the collimating or subsidiary telescope in a horizontal position, a method which though characterized by him as the best mode of using a level that has yet been devised, is still liable to the objections urged against levels in general.

Dr. Brinkley, in this communication, states a number of observations made with the floating collimator of Captain Kater, as applied to the Dublin circle, in which he observes it affords the means of ascertaining the index error with as great precision as by reversion, and that in several points of view it is undoubtedly superior to that method. The reversing principle of the Dublin circle, he observes. Serves very conveniently for a measure of the accuracy of the floating collimator, and serves to show very satisfactorily, that applying this instrument to any circle will introduce no error depending on the collimator itself. The author regards the results of these observations as highly favourable to the principle of the collimator, which he considers as a new astronomical power, and as even belonging to a more advanced era of practical astronomy than the present.

The author begins this paper by an enumeration of the various works on the subject extant in our language, and a general mention of the writings of foreign mathematicians, which he considers as leaving room for further inquiry and simplification. He then states the method employed in his experiments for determining the refractive and relative dispersive powers of his glasses, the former of which is that generally known and practised;—of measuring the radii and focal length of a lens, and thence deriving the refractive index; with some refinements in its practical application, consisting chiefly in using the lens as the object-glass of a telescope, and adapting to it a positive eye-piece and cross-wires, which are brought precisely to the true focus by the criterion of the evanescence of parallax arising from a motion of the eye, as is practised in adjusting the stops of astronomical instruments. The only source of error it involves is in the measurement of radii of the tools which it was found could always be performed within 1/500th of their whole values. The dispersive ratio of two glasses was determined by over-correcting the dispersion of a convex lens of the less dispersive glass by a concave of the greater, and then withdrawing the latter from the former till the achromaticity is perfect, or as nearly so as the materials will admit, and measuring the interval between the lenses and their foci, from which data the ratio of their dispersive powers is easily obtained. The refractive indices and dispersive ratio thus determined, the next step is to find the radii of curvature so as to destroy spherical -aberration. In this investigation, the author does not consider it as necessary to limit the indeterminate problem by any further condition, as others before him have done, but regarding it as a matter of great convenience to avoid contact of the interior surfaces in the centre of the glasses, leaves it open to the optician to make a choice within certain limits, thus avoiding what he considers as an intricate equation arising out of the fourth condition. He proceeds, therefore, to express analytically the aberrations of the glasses, and to deduce the equation expressive of its destruction, which of course involves one indeterminate quantity; this may be either of the radii, or any combination of them. The author chooses the ratio of the radii of the interior and exterior surfaces of his flint lens for this indeterminate, which he assumes, as well as may be, to satisfy the condition of the absence of contact and near equi-curvature of the adjacent surfaces; thence deduces, first, the radii of both of the surfaces of the flint lens; next, its aberration to be corrected; and thence, by the solution of a quadratic, or by the use of a table containing its solutions registered in various states of the data, the ratio of the radii of the convex, whence the radii themselves are easily deduced.

The idea of constructing achromatic telescopes with fluid lenses was first suggested to the author by the attempt of Messrs. Gilbert to apply to practice the principles and rules for the construction of aplanatic object-glasses, laid down by Mr. Herschel in the Philosophical Transactions for 1821. In following these suggestions, the author became sensible of the difficulty of obtaining flint glass of sufficient size and purity for astronomical telescopes; and was thence led to consider the possibility of substituting some fluid in place of flint glass. Dr. Blair had, many years ago, succeeded in making very perfect telescopes of this description, but he still retained the use of flint glass. Among the various fluids adapted to this optical purpose, the author gave a decided preference to the sulphuret of carbon, which combines properties of perfect transparency and freedom from colour, with a refractive index nearly equal to that of flint glass, and with a dispersive power more than double, properties which it appears to retain under all the temperatures to which it is likely to be exposed in an astronomical telescope. After several trials, Mr. Barlow determined the best method of confining this fluid, but was at first unsuccessful in his attempts to construct with it a telescope of 6 inches aperture and 7 feet in length. He afterwards undertook a smaller one of 3 inches aperture, which he at length accomplished, and in the very first trials with it was able to separate a great number of double stars of the class which Sir William Herschel has pointed out as tests of a good 3½-inch refractor. Encouraged by his success, he again attempted a 6-inch object-glass, with a different manner of adjusting and securing the lenses, and considers the result of his endeavour as proving at least the practicability of the construction. This instrument, with a power of 143, shows the small star in Polaris so distinct and brilliant, that its transit might be taken with the utmost certainty; it exhibits distinctly the small stars in α Lyræ, Aldebaran, Rigel, &c. and decidedly separates Castor, γ Leonis, and ϵ Bootis. The belts and double ring of Saturn are well exhibited with a power of 150; and the belts and satellites of Jupiter are tolerably defined with the same power, but will not bear a higher power than about 200. In the usual construction of achromatic telescopes, the two or the three lenses composing the object-glass are brought into immediate contact. But the high dispersive power of the sulphuret of carbon enables Mr. Barlow to place the fluid correcting lens at a distance from the plate object lens equal to half its focal length. By this means the fluid lens, which is the most difficult part of the construction, is reduced to one half or less of the size of the plate lens. This construction, therefore, renders us independent of flint glass, enables us to increase the aperture of the telescope to a considerable extent; and gives us all the light, field, and focal power of a telescope of one and a half time the length of the tube. The author investigates analytically the formulæ for calculating the proper distance of the lenses on this construction, and expresses a hope that further experiments will enable us to determine the precise distance which shall reduce what has been termed the secondary spectrum, inseparable from the ordinary construction, either to zero, or to an inconsiderable amount.

In a paper lately read to the Society, the author stated that he had not perceived any change in the focal length of the telescope, induced by changes of temperature; but he has since ascertained that in order to produce the brightest and most perfect image, the distance of the object-glass requires a minute adjustment, amounting to 0·134 of an inch, corresponding to an elevation of temperature from 57° to 84°, or a depression from 57° to 31°. In order to introduce greater clearness and precision, the author proceeds to define certain terms which he finds it necessary to employ. By the length of the telescope , he would be understood to mean the distance between the object-glass and the focus; by the fluid focus , that between the fluid lens and the focus; and by the focal power of the telescope, he means the focal length of a telescope of the usual construction, which gives the same convergency to the rays, or produces an image of the same size: but he also employs the term focal length of the telescope , as synonymous with the first; that of fluid focal length as synonymous with the second; and that of equivalent focal length as synonymous with the last of these terms.

The author, after noticing the peculiarities discovered by Walsh in the electricity of the Torpedo, and the opinion of Cavendish, that it resembles the action of an electrical battery weakly charged, adverts to the conjecture of Volta, who considered it as similar to that of the galvanic pile. Being on the coast of the Mediterranean in 1814 and 1815, the author, desirous of ascertaining the justness of Volta’s comparison, passed the shocks given by living torpedos through the interrupted circuit made by silver wire through water, but could not perceive the slightest decomposition of that fluid; the same shocks made to pass through a fine silver wire, less than one thousandth of an inch in diameter, did not produce ignition. Volta, to whom the author communicated the results of these experiments, considered the conditions of the organs of the torpedo to be best represented by a pile, of which the fluid substance was a very imperfect conductor, such as honey, and which, though it communicated weak shocks, yet did not decompose water. The author also ascertained that the electrical shocks of the torpedo, even when powerful, produced no sensible effect on an extremely delicate magnetic electrometer. He explains these negative results by supposing that the motion of the electricity in the torpedinal organ is in no measurable time, and wants that continuity of current requisite for the production of magnetic effects.

The principles on which the reflecting, and also the achromatic refracting telescope are constructed, have been recently applied with considerable success to the microscope, and have added much to the power of that instrument. The author speaks with much commendation of the peculiar construction adopted in Mr. Tulley’s compound achromatic microscopes, consisting of a combination of object-glasses of short focus and large aperture, the curvatures of which are such as very nearly to equalize the refractions produced by each. As the magnitude of the aperture, he observes, is valuable only in proportion to that of the pencil of light which it admits, the latter circumstance is that which chiefly claims attention; and as it is often erroneously estimated, a method is pointed out of ascertaining it with sufficient exactness for every practical purpose. He then enters into a detailed description of the several parts of an instrument in his possession constructed on the principles he recommends, referring to the drawings which accompany the paper. The magnifying power may be varied at pleasure, either by drawing out the tubes containing the eye-pieces, or by substituting an eye-glass of different power, or differently combined; and by these changes an uninterrupted range of amplification is obtained from 35 to 800 diameters. No sensible difference as to distinctness is observable, whether the effect is produced by changing the eye-piece, or varying the length of the tubes. The construction of the' instrument admits of the utmost variation of magnifying power without the risk of losing sight of the object viewed : and every part which relates to the illumination being wholly detached from the stage, ample opportunity is afforded of rapidly moving the objects, and bringing into view a succession of them, while the light remains the same. Minute directions are given for the employment of the instrument, and its application to various purposes; and great stress is laid on the importance of a skilful management of the light. In stating the results of his experience on this subject, the author takes occasion to advert to some of the sources of fallacy by which incautious observers with the microscope have so often been greatly misled. When a pencil of rays proceeding from an indefinitely small bright portion of an object is brought to a focus by the most perfect object-glass, the image thus formed is in reality not a point, but a small circle, and will always appear as such if the eye-glass of the microscope be sufficiently powerful. These circles have a considerable analogy to the spurious discs of stars viewed through telescopes. Like the latter, they become much enlarged by diminishing the aperture of the object-glass; and they are also enlarged by increasing the intensity of the illumination. The overlapping of contiguous circles of diffusion has given rise to many fallacious appearances; such as the spottiness which some surfaces assume, and which has been mistaken for globules. This optical illusion has been the basis of some ingenious but visionary speculations on the intimate structure of organic matter. The appearance, in certain directions of the light, of lines on the surface of an object, where they do not really exist, may be traced to a similar cause.

In a paper which I communicated to this Society in 1815, and which was published in the Seventh volume of their Transactions, I described a new species of coloured fringes, produced between two plates of parallel glass. From a consideration of the theory of this class of phenomena, it was obvious that analogous, though much more complicated, systems of rings should be produced between plates with curved surfaces, but it was not till 1822 that I succeeded in detecting them; and so completely are these rings concealed by the superposition of similarly situated images, that, in consequence, of having forgotten my method of observation, I have experienced the greatest difficulty in rediscovering them.My earliest experiments were performed with a double achromatic object-glass, made by Berge, having a diameter of inches, and 30 inches in focal length. The inner surfaces of the crown and flint glass lenses were ground to different radii, as shewn in the section of it at AB, CD, Fig. 5, Plate IX.; and the outer surface of the flint-glass lens was concave, so that there was left between the lenses a meniscus of air A 2, B 3 A.

The great advantage which has attended Mr. Dollond’s ingenious application of the negative achromatic lens to the micrometer eyepiece, seems to make it desirable that the principles on which that lens is constructed, and its general application, should be more fully illustrated than is done in the short extract made from my letter to Mr. Dollond, and given by him in his recent paper in the Philosophical Transactions. In my original fluid telescope, the negative lens was employed for the double purpose of lengthening out the focus and correcting the colour of the front lens; and the great advantage of the lengthening principle was manifested by the high penetrating power of the instrument in the centre of the field. Unfortunately, however, the perfect part of this was very limited, so that when Mr. Dollond constructed the second telescope for the Royal Society, I gave up this advantage for the sake of enlarging the held; but I found that by this means much of the penetrating power of the former telescope was lost; for although I had the same aperture, many small stars which were before very perspicuous were in this instrument seen only with difficulty and under advantageous circumstances of weather, absence of moonlight, &c.

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The principle of the instrument here described is the unequal expansion of different metals by heat. A bar of zinc, alloyed with four or five per cent, of copper, and one of tin, about an inch in breadth, one quarter of an inch thick, and two feet long, is firmly and closely riveted along its face to the face of a similar bar of steel of about one third in thickness. The product of the rigidity and strength should be nearly the same, so that the texture of each may pretty equally resist the strains of flexure. Twelve such compound bars are united in pairs by a hinge joint at each of their ends; having the zinc or alloy bars fronting one another. At ordinary temperatures these bars will be parallel, and nearly in contact; but when heated, they bend outwards, receding from each other at their middle parts, like two bows tied together at their ends. When a more considerable expansion is wanted, a series of such bars is laid one over the other. The movement thus resulting is applied by the author in various ways to regulate the opening of dampers, letting in either cold air or cold water, or closing the draught of a fireplace, as the case may be. He proposes its employment to regulate the safety valves of steam boilers, as working with more certainty than the common expedients.

The Reports received by the Secretaries, from Sir John Herschel, Professor Airy, and Captain Smyth, on the Fluid-lens Telescope constructed for the Royal Society on Mr. Barlow’s principles, were, by direction of His Royal Highness the President and Council, read to the Society at this meeting. Sir John Herschel's Report. I have seen Mr. Barlow’s telescope at Cambridge, and examined it on several objects, in a very fine night, the 25th (if I remember) of June. As I have now no time to give it any further trial at Slough, (where I have no longer, either, any achromatic telescope of sufficient power to compare it with, all my apparatus being dismounted and in course of packing,) I will here state in few words, as my report on it, all I could then collect relative to its action. 1. Achromaticity .—Mr. Barlow’s telescope is remarkably free from the dispersion of colour, very much more so than I could have expected from the nature of the correcting medium, and nearly or quite as much as could be desired.

The application of a concave achromatic lens to the wired micrometer of a telescope, arose out of the series of trials that were made for the purpose of correcting the aberrations of the eye-glasses applied to the telescope constructed by the author for the Royal Society, with a fluid-correcting lens, on the plan suggested by Professor Barlow. The concave lens, being interposed between the object-glass and the eye-glass, and being at the same time achromatic, combines the advantages of doubling the magnifying power, without a corresponding diminution of light, and without altering the apparent distances of the threads of the micrometer. The results of the trials made with telescopes to which this addition was made, are given in a letter to the author from the Rev. W. R. Dawes, of Ormskirk; from which it appears that Mr. Dollond’s method was attended with complete success. Mr. Dawes states, that, in order to put its illuminating power to a severe test, he had examined with this instrument the satellites of Saturn and the minute companion of k Geminorum, but could discover no decided difference in the apparent brightness of the former, allowance being made for the difference in the power employed; and the latter star was seen quite as distinctly with a much smaller power. Extracts are subjoined from a letter of Professor Barlow’s to the author, containing formulæ for the construction of the lens.

Respecting the air in question, which Dr. Davy had found to consist of about 80 per cent, of azote and 10 oxygen, he had remarked that two views might be taken of its origin; the one, that it was of volcanic source; the other, that it was derived from the sea water, and merely disengaged by the heat of the volcano. Dr. Davy, rejecting the former of these views, had adopted the latter, for reasons, the validity of which was controverted by Dr. Daubeny; and the purpose of the present paper is to answer the objections urged against them, and to bring additional evidence in support of his opinion.

The first part of this paper is occupied by an investigation of the circumstances attending the fœtal development of the Torpedo. In the first stage of embryonic growth which the author had an oppor­tunity of observing, when the embryo was about seven tenths of an inch in length, it had neither fins nor electrical organs, nor any ap­pearance of eyes; it exhibited short external branchial filaments, not yet carrying red blood; and there was a red spot in the situation of the heart, communicating by red vessels in the umbilical cord with the vascular part of the egg. There is no membrane investing the fœtus, as is the case with some species of Squall ; nor any fluid in the uterine cavity; neither could the author find any urea or Iithic acid in that cavity. By taking the mean of many observations, it appeared that the weight of the egg, before any appearance of the embryo, is 182 grs., and after its appearance, including the weight of the latter, 177 grs.; while the weight of the mature fish is about 479 grs.; showing an augmentation of more than double. Thus it differs remarkably, in this respect, from the fœtal chick, which at its full time weighs consider­ably less than the original yolk and white from which it is formed. No communication can be traced between the fœtus of the Torpedo and the parent, through the medium of any vascular or celiular structure; and the stomach of the former is always found empty. Hence the only apparent source of nourishment is absorption from the surface; and the author states his reasons for believing that the branchial fila­ments are the principal absorbing organs, the materials they receive being chiefly employed in the construction of the electrical organs, while those which enter into the composition of the body generally are absorbed by the general surface of the fœtus. The author is led, from his researches, to the conclusion that the mode of reproduction in the Torpedo is intermediate between the viviparous and the ovoviviparous. In the second part of the paper, the author discusses the question as to the number of species of the genus Torpedo existing in the Mediterranean; and concludes that there are only two, viz. the Ochiatella and the Tremola .

Dr. Davy complains that Mr. Faraday has, in the paper referred to, made certain statements with respect to the opinions of Sir Humphry Davy relative to the conducting powers of dry nitre, and caustic potash and soda, when in fusion by heat, and also with regard to other matters connected with voltaic electricity, wdiich are not correct; and vindicates Sir Humphry Davy from the charge of want of perspicuity in the statement of his views of these subjects. A Note by Mr. Faraday on the preceding Remarks by Dr. Davy was then read, in which he replies to the charges there brought forward, and justifies those statements, the accuracy of which had been impugned by Dr. Davy.

This report commences with a description of the iron steam-vessel, the “Garryowen,” belonging to the City of Dublin Steam Packet Company, and built by the Messrs. Laird, of Liverpool. She is constructed of malleable iron, is 281 tons burthen, and draws only 5 1/4 feet water, although the weight of iron in the hull, machinery, &c. is 180 tons. This vessel was placed under the directions of the author, in Tarbert Bay, on the Shannon, on the 19th of October, 1835, for the purpose of investigating its local attractions on the compass. The methods which were adopted with that view are given ; together with tables of the results of the several experiments, and plans of the various parts of the Garryowen. The horizontal deflections of the magnetic needle at different situations in the vessel were observed, for the purpose of ascertaining the most advantageous place for a steering compass, and also for the application of Professor Barlow’s correcting plate : and the dip and intensity in these situations were, at the same time, noted.

The method employed by the author for obtaining, by a combination of lenses, the convergence to foci of the colorific solar rays, together with the dispersion of the calorific rays, consists in making a beam of solar light, which contains both kinds of rays, pass, after it has been converged to a focus by a convex condensing lens, through a second convex lens, placed at a certain distance beyond that focus: that distance being so adjusted as that the calorific rays, which, from their smaller refrangibility, are collected into a focus more remote from the first lens than the colorific rays, and consequently nearer to the second lens, shall, on emerging from the latter, be either parallel or divergent; while the colorific rays, which, being more refrangible, had been collected into a focus nearer to the first lens, and more distant from the second, will be rendered convergent by this second lens; so that the second focus, into which they are thus collected, will exhibit a brilliant light without manifesting any sensible degree of heat. The light so obtained may be advantageously applied to the solar, and to the oxy-hydrogen microscopes, from its producing no injurious effects on objects inclosed in Canada balsam, or even on living animalcules exposed to its influence. Another improvement in the construction of the microscope employed by the author, consists in the cell for holding objects being made to move quite independently of the field glass; so that the best focus is obtained by an adjustment which does not disturb the field of view.

Mr. T. P. Teale, F.L.S., then read his paper “On the Fossil Ichthyology of the Yorkshire Coal Field.” He began by saying that the title of the West-Riding Geological and Polytechnic Society sufficiently explained its principal objects, namely, Theoretical Geology and Practical Mining. The former, the science which investigates the laws whereby were regulated the original deposition and the subsequent disturbances of the stratified rocks; the latter, the art which renders available to man the stores of mineral treasure provided by an all-wise and beneficent Creator for alleviating the wants and for ministering to the comforts of his creatures. These two departments, although often separately pursued, are nevertheless capable of being rendered mutually subservient to each other’s advancement. Thus, whilst the daily labours of the miner are disclosing new facts upon which the geologist builds his theories, the generalizations of the geologist direct the proceedings of the miner, and save the enormous waste of time and capital which has so repeatedly attended mining efforts when unaided by the the light of geological science. Within the sphere of the Society’s operations, there are few objects of greater practical importance than the identification of strata. It was formerly imagined that the valuable beds of coal worked at Middleton, Haigh Moor, and Lofthouse, in this neighbourhood, were identical; but it has now been demonstrated, by means of this Society, that the main-coal of Middleton is not identical with that of Haigh Moor and Lofthouse. But he understood that all are not yet agreed ...

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The Rev. Dr. Scoresby, after a few introductory observations, remarked that he might have occasion to refer very briefly to the principle of the instrument as necessary to the illustration of his subject. For the information of those who might not be aware of the construction of the telescope, he would observe that the principle upon which it acted was this, —it simply depended upon the property of a convex glass and of concave reflectors, which produce an image at their focus. For instance, if he had a magnifying glass, and admitted the light through that, more particularly in the way of the camera obscura, there would be an image of the object formed at the other end. That image would be in proportion to the focal length of the glass, so that the telescope which had the longest focal distance would magnify the best. It is the area or surface of the glass, or the metal, which gives the quantity of light, but a speculum of one-inch size will produce the same magnifying power if the focal length is fifty-four feet, as the six feet telescope of Lord Rosse. The only other thing with reference to the principle was the examination of the object, which can be shown by a simple experiment with a lantern or candle. If, for instance, he placed a magnifying glass near a candle or a lamp, he would have thrown on a piece of paper the image of the candle inverted. The forms of ...

The Rev. William Thorp, B.A., next proceeded to describe the chief features of a New Safety Lamp, which was expected effectually to remedy all the defects of the lamp of Sir Humphry Davy, affording five times as much light, and being perfectly safe in every condition of coal mines. One of the principal defects to be obviated in the old Davy lamp consisted in its affording too little light,—and hence the temptation to miners to endeavour to gain an increase at any risk to themselves. While some frequently prefer to work with a candle, in constant danger, rather than use it, others are in the habit of removing the gauze to attain the same object; both of which expedients are well known to be fraught with the most disastrous consequences. In addition to which, the Davy is insecure, as well as all other lamps applied to coal mining, as proved by the Report of the Miners’ Association of Newcastle, in 1835, furnished to the Parliamentary Committee. Charles Morton, Esq., moved, and Thomas Wilson, Esq., seconded, “That the thanks of this Meeting be given to the gentlemen who have read Papers before the Society this day.” Henry Briggs, Esq., moved, and Dr. Wm. Alexander seconded, “That the thanks of the Meeting be given to the Vicar of Huddersfield, for his able services in the Chair.”

In this communication the author describes a series of experiments, made for the purpose of determining the distribution of the voltaic force from its source in the generating metal, as indicated by the de­position of reduced copper in the constant battery; and, considering that the voltaic combination most perfect in theory would be one formed by a solid sphere, or point, of the generating metal, sur­rounded by a hollow sphere of the conducting metal, with an inter­vening liquid electrolyte, he constructed an apparatus making as near an approximation as possible to these conditions. It consisted of two hollow brass hemispheres, applied to each other by exterior flanges, and rendered water-tight by an intervening collar of leather. In the centre of the hollow sphere thus formed, a ball of amalgamated zinc was suspended by a well-varnished copper wire, connected with one of the cups of a galvanometer, and was contained in a mem­branous bag holding the acid solution ; the whole being introduced through a short tube in the top of the upper hemisphere, and the remaining space being filled with a saturated solution of sulphate of copper. The galvanic circuit was completed by wires establishing connexions between either hemisphere and the other cup of the galva­nometer. For measuring the forces developed, sometimes the ordi­nary magnetic, but in the greater number of instances the calorific galvanometer of De la Rive was employed; the indications given by these instruments were noted, on the completion of the circuit, in various ways; and the deposition of copper in the hemispheres was examined after the apparatus had been in action for a certain number of hours. The following are the conclusions which the author deduced from a series of experiments thus conducted: 1st. The force emanating from the active zinc centre diffuses itself over every part of the upper hemisphere, from which there is a good conducting passage for its circulation.

In the instrument here described, there is provided, in addition to the ordinary barometric tube (inverted, in the usual way, in a cistern of mercury,) a second tube of the same dimensions, placed by the side of the former, and likewise filled with mercury, but only to the height of twenty-eight inches above the level of the mercury of the cistern. This tube is closed at its lower end, and fixed to a float supported by the mercury in the cistern: and it bears, at its upper end, an ivory scale, three inches in length. The elevation of the mercury in the barometric tube is estimated by the difference between its level and that of the mercury in the closed tube; and is measured on the ivory scale by the aid of a horizontal index, embracing both the tubes, and sliding vertically along them. As the float which bears the closed tube, to which the scale is attached, rests freely on the mercury in the cistern, and consequently always adjusts itself to the level of that fluid, no correction for the zero point is needed; and as every change of temperature must similarly affect the columns of mercury in both the tubes, after the scale has been adjusted so as to read correctly at any given temperature, such as 32°, which may be effected by comparison with a standard barometer, every other reading will correspond to the same temperature, and will require no correction. The author considers the error arising from the difference of expansion corresponding to the different lengths of the two columns of mercury, and which will rarely amount to one four-hundredth of an inch, as too small to deserve attention in practice, being, in fact, far within the limits of error in ordinary observations. Subjoined to the above paper is a letter from the author to Sir John Herschel, containing a statement of comparative observations made with a mountain barometer, and with the compensation barometer, from which it appears that the use of the latter is attended with the saving of a great quantity of troublesome calculation. The comparative observations are given in a table, exhibiting a range of differences from +˙012 to -˙016 of an inch.

The author observes, that experience has shown it to be impracticable to make a telescope even approach to achromatism, by employing the same object-glass with an astronomical, as with a terrestrial eye-piece: for if the focus of the blue rays from the object-glass be thrown forwards, as it must be in order to make it impinge upon the focus of the blue rays of the terrestrial eye-glass, then there will be produced a great over-covrection for the astronomical eye-glass; and vice versa . Hence it appears that the application of Huyghenian eye-pieces to refracting telescopes, is incompatible with the conditions of achromatism, throughout the entire range of magnifying power; and that in reflecting telescopes they unavoidably introduce dispersion, because they are not in themselves achromatic. These defects the author proposes wholly to obviate, by substituting for the Huyghenian eye-pieces, single achromatic lenses of corresponding magnifying power; consisting of the well-known combination of the crown-lens, and its correcting flint-lens, having their adjacent surfaces cemented together; thus avoiding internal reflections, and enabling them to act as a single lens. The achromatic eye-pieces which he uses were made by Messrs. Tulley and Ross, and are of the description usually termed single cemented triples .

The author’s attention having been long directed to the remarkable fact, that odour, resembling that of phosphorus, is given off during the escape of positive electricity from the point of a conductor into air; and is likewise perceptible when lightning has struck any object, and also when water is electrolyzed, he has investigated the circumstances attending these phenomena; and the results he has obtained will, he expects, afford a clue to the discovery of their cause. The odour which accompanies the electrolyzation of water, he observes, is only disengaged at the positive electrode. He also finds that the odoriferous principle can be preserved in well-closed glass bottles for any length of time. The only metals which yield this odour are gold and platina; but dilute sulphuric, phosphoric, and nitric acids, and from aqueous solutions of several of the salts, also disengage it. Raising the temperature of the fluid to the boiling point prevents the odour from arising; and the addition of comparatively small quantities of powdered charcoal, iron, zinc, tin, lead, antimony, bismuth or arsenic, or of a few drops of mercury, to the odorous principle contained in a bottle, immediately destroys the smell; and the same happens when platina or gold, heated red hot, is introduced into the vessel containing that volatile substance.

The experiments described in this paper were made on a single fish, of middle size, recently taken out of the water. Portions of the electrical organs, cut transversely in thin slices, exhibited under the microscope many elliptical particles, apparently blood-corpuscles, the long diameter of which was about 1-800th, and the short about 1-1000th of an inch, and a few filaments, apparently nervous, irregularly scattered; some of them tortuous, and all about the 2000th of an inch in diameter. The latter bore no resemblance to muscular fibres. The blood contained some globular particles, having a diameter of the 4000th of an inch, mixed with the elliptical. The mucus for lubricating the surface was found to contain globules apparently homogeneous in substance, but of irregular outline, and in size varying from the 2000th to the 270th of an inch.

Design of analog and digital electronic circuits is an integral part of the electrical engineering curriculum. Software tools, which enable design, simulation, measuring and circuit analysis as well as PCB (Printed Circuit Board) design, are called EDA (Electronic Design Automation). The paper describes the introduction of EDA software in the first semester of the professional study of electrical engineering at the Zagreb University of Applied Sciences within course Personal Computers in Electrical Engineering. Examples of laboratory exercises related to electrical circuit diagrams, use of component libraries, work in standard laboratory environment (power supplies, function generators, voltmeters, ammeters, oscilloscopes, etc.), circuit analysis in a DC and AC mode as well as in time and frequency domain are described. Focus is on the optimal implementation of EDA tool NI Multisim and its integration with the existing learning management system Moodle as a platform for exercise learning and knowledge assessment.

Currently, solidification/stabilization (S/S) is the most widely used pretreatment measure for sewage sludge prior to its disposal in landfills in China. Looking for an effective measure to increase the early strength of the solidified sludge has become a significant requirement for the sludge treatment market. In this study, the chemical and mechanical behaviors of the sludge samples treated by sulphoaluminate cement (SC) and ordinary portland cement (OPC) were investigated and compared by testing the nonevaporable water (NEW) and unconfined compressive strength (UCS) of the solidified sludge. This was followed by conducting scanning electron microscopy (SEM) analysis. From the perspective of the conversion of NEW, the retardation mechanisms of the hydrating reaction for the SC and OPC used in the sludge were also studied. The results showed that SC is an excellent cementitious additive with high early strength in S/S treatment for sewage sludge—much better than OPC, which is currently commonly u...

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