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The paper presents a project of a prototype solution of a device for making inseparable crimped joints consisting in forming the material of two elements to be joined to each other with the use of punches. The work contains the assessment and analysis of the joints made in the stand with the use of various forming tools. Furthermore, the paper presents the analysis of the characteristic features of the new joints, as well as dependences in strength tests. The elements joined on the machine had been made of 5754 aluminium. This material and the presented joint are used in the construction of heat exchangers, such as water, oil coolers or condensers in the automotive or aircraft branch.

In this paper we present a parametric method for the identification of a horizontal positioning system for a billets unloading machine. The input-output models are obtained on the experimental models and on the priori information of the process. The obtained models are represented as second-order underdamped systems. The assessment of the models is made via simulation and a best fit model follows. In order to improve the current process performances, new automatic control structures for the positioning process can be derived using the determined model

Delivering reliable service requires satisfactory operation of numerous line components, spanning significant geographical areas and subject to environmental, electrical, and mechanical stresses, plus normal aging. Conventional reliability practices use periodic maintenance to minimize failures, coupled with rapid restoration procedures when outages occur. Reliability statistics have shown little change in decades. Newer technologies can shorten outages, by automatically rerouting service to customers on healthy feeder segments, but they: require redundant paths for power flow; react only after outages occur; and often require communications with pole-mounted switches. Over the past decade, Texas A&M University has demonstrated that electrical waveforms, available via conventional substation-based CTs and PTs, contain evidence of failures, incipient failures, and improper operation of feeder equipment, often well before these conditions escalate and cause outages. This provides the basis for conditioned-based maintenance and outage avoidance. This paper provides examples, from operating feeders, demonstrating some of these advances.

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.

Pressure regulators have a great impact on the runtime and energy savings of supersonic wind tunnels. In order to investigate this impact quantitatively the theoretical isentropic (ideal) equations for the supersonic wind tunnel flow were compared with viscous CFD computations. The theoretical model was extended include the flow from the outflow from the pressure vessel up to the wind tunnel. This theoretical model was solved with and without pressure regulation valve using a Runge-Kutta method. The differences in runtime and energy consumption for both configurations with and without pressure regulator as well as the derivation of the analytical model and the numerical solution are presented in detail in this paper.

Recently the microstrip patch antennas (MPA) has evolved into a most dynamic and indigenous field in the arena of UWB demanding low profile and mini antennas with ample frequency choice for ultra wide (UWB) applications. Thus the paper focuses on thorough analysis of a novel rectangular microstrip patch with carpet shaped fractal antenna fed by microstrip line for applications in Ultra- Wideband. The basic antenna structure is rectangular microstrip patch which is modified by adding slotted rectangular shape with partial ground plane at the rear end is iterated using fractal geometry that exhibits more bandwidth and reduce return loss. The proposed antenna has a compact size 50×42mm2 with height 1.6mm and designed on low cost FR4 (er = 4.3) substrate. A wider bandwidth (-10 dB) of around 3.1 – 8.25 GHz with stable radiation pattern is achieved and E-field, H-field current distributions are also examined. When compared with the existing traditional UWB antennas, the recommended antenna exhibits good characteristics, low profile and more so cost-effective. By using CST MW studio software the Proposed UWB antenna is designed and simulated to verify antenna parameters for improvements.

Investment decisions in the development and production of new aircraft models is difficult because of the technical and market uncertainties associated with such a complex process. The accompanying risks can be mitigated through a flexible approach that incorporates several decision points at different stages of the process. Therefore, as the project evolves, management will be able to diagnose its progress, compare it to previous expectations, and decide to continue or not. In this paper, we present a methodology to evaluate flexible business strategies that is based on real options analysis (ROA) and Monte Carlo simulation. This methodology takes into account the flexibility that managers have to affect the success of any given project and, therefore, it provides a better estimate of project value. Numerical results are given for a representative process based on actual aircraft manufacturer's data.

Windows 95 may provide a major stimulus to Intelligent Network (IN) development, to real technological convergence between computing and telecommunication, and to a major reordering of research priorities in the field. The paper examines IN in the context of the evolution of convergence and the larger framework of information superhighway, infrastructure and society developments. It shows how the pace and direction of IN development will be driven by demand associated with organisational and institutional change, not the simple supply of greater capacity or the discovery of ‘killer applications’. This will be associated with a shift in priorities to distributed networking, information-based service development and a diversity of very specific new applications.

Air quality and fuel efficiency has become important factors in decision-makings on urban traffic planning and management. To support the process, simulation models have potential to play essential roles in evaluation of planning alternatives and control strategies. However, traffic and its environmental impacts are different processes and often require various levels of models. With concerns on high computing performance and rich functionalities, it may be not appropriate to model emission inventory within traffic simulation. In this paper, we present a distributed simulation approach, and an independent emission/energy computing platform is built to simulate, visualize and analyze online emission outputs, given a microscopic traffic simulation tool, KTH-TPMA. Two distributed computing frameworks, common objects request broker architecture (CORBA) and service oriented architecture (SOA), are adopted in the distributed software design and implementation. Several emission models are implemented and generally evaluated in micro simulation runs of two road networks.

Water distribution network that includes supply reservoirs, overhead tanks, consumer demand nodes, interconnecting pipes, lifting pumps, and control valves is the main mode of water supply for majority of the communities especially in urban areas. Supply of required quantity of water and at right time is the primary objective of water distribution network analysis. The analysis of water distribution networks can be broadly classified into design and operation problems and both problems have been the focus of many researchers over the past three decades. In the water distribution network design problems, the target is attaining the cost effective configuration that satisfies the minimum hydraulic head requirement at the demand nodes. In this paper, a new algorithm for design of water distribution network namely "heuristics-based algorithm" which completely utilizes the implicit information associated with the water distribution network to be designed has been proposed and validated with two water distribution networks. It is found that the proposed algorithm performs well for the least-cost design of water distribution networks. � 2009 ASCE.

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.

The paper systematically studies the impact of the 3d transition metals Ti, V, Cr, Mn, Fe, Ni and Cu on electrochemical stability of non-passivated cobalt-base alloys {0 0 0 1} surface by evaluating the chemical potential and the electrode potential shift relative to pure cobalt metal using density functional theory calculations. Cr, Fe, Mn, and V are found to make the Co atoms more stable on the {0 0 0 1} surfaces of the corresponding alloys compared to pure Co {0 0 0 1} surfaces, whereas Ti, Ni, and Cu make Co atoms much less stable. Among all the considered alloying elements, chrome is the most beneficial to the stability enhancement of alloys. Furthermore, the effects of water and hydroxyl adsorption on the electrochemical stability are considered. It is found that the surface adsorption properties may be considerably modified by introducing the Cr atoms. Our results indicate that water or hydroxyl adsorption destabilizes both the Co–Cr alloy and pure Co surface. However, the Co–Cr alloy surface is still more stable than the pure Co surface in the presence of adsorbed water, while the pure Co surface is more stable than the Co–Cr alloy surface in the presence of adsorbed hydroxyl. Our calculation reveals that the electrochemical corrosion property of the Co–Cr alloy is insensitive to water adsorption and sensitive to hydroxyl adsorption in comparison with the pure Co metal.

Texas Instruments has been developing a passive tag which removes some of the practical difficulties, meeting the optimum cost/performance trade off and performance requirements for two dedicated market sectors. In the form of a "smart label" the transponder electronics have been laminated into paper labels and plastic cards and this product is called Tag-it/sup TM/. This passive transponder has been developed for the target markets of express parcels and airline baggage though, over time, we expect that it will be adapted for use in other market sectors. In these two markets a flexible label is required where it can meet existing label specifications and form factors and be easily introduced into existing hardware.

The proliferation of antipersonnel landmine use has created problems world-wide. This study identifies and clarifies the complex issues that have created the current landmine dilemma. In addition, this research discusses international and Congressional attempts to regulate antipersonnel landmine use and critically analyzes these efforts. This paper also proposes recommendations as to what the role of the United States should be in resolving the land mine dilemma.

This paper examines the dynamic stability of a notional Mars entry vehicle augmented with an attached supersonic inflatable aerodynamic decelerator (SIAD) deployed at Mach 5. Dynamics of the attached isotensoid and tension cone SIAD configurations are compared using an explicit solution to the planar equations of motion. A current experimental database of flexible isotensoid and tension cone static aerodynamics is employed in the simulation. Pitch-damping data from the Mars Science Laboratory (MSL) ballistic range tests is parameterized and applied to the SIAD-augmented portion of flight. The Mach number at which safe parachute deployment can occur depends on the amplitude of pitch oscillation, so the sensitivity of this metric to the parameterized pitch-damping behavior is determined. Pitch dynamics yielding unacceptable parachute staging conditions are quantified to inform SIAD configuration selection and design. These exploratory results are used to recommend a general strategy for measuring the pitch dynamics of SIAD-augmented blunt vehicles in ground testing facilities.

Insurance telematics is a disruptive technology that is expected to reform the vehicle insurance industry. Based on sensor data, the traditional measures for calculating the insurance premium are complemented to determine a fee that more accurately predicts the risk profile of the policyholder. From an instrumentation and measurement point of view, there are several insurance telematics challenges that have to be tackled. It is about consistently extracting relevant figures of merit (FoMs) like number of harsh braking, speeding, heavy cornering, trip smoothness, etc, and then to transform these FoMs into a valid measure, or score, that determines the risk profile of the insurance customer. The paper presents a characterization of FoMs in terms of actuarial relevance, the driver's influence, stationarity and observability, which are important for the given task. Dedicated hardware to be fitted into the on-board diagnostics outlet as well as contemporary smartphones are two different insurance telematics platforms for data collection. The paper discusses the properties of the smartphone in the perspective of insurance telematics as a low-cost alternative to the hardwired platforms like the one connected to the vehicle's on-board diagnostics outlet.

(1798). XXI. Chemical experiments respecting different methods of rendering paper and the writing on it indestructible by fire. The Philosophical Magazine: Vol. 1, No. 1, pp. 89-92.

(1800). III. On the origin and progress of the manufacture of pig-iron with pit-coal; and comparison of the value and effects of pit-coal, wood, and peat-char. The Philosophical Magazine: Vol. 7, No. 25, pp. 35-46.

The subject of the means of producing artificial cold, or the constitution of frigorific mixtures, I had considered as exhausted, in the Papers I have already had the honour to lay before this Society : so far as relates to that part of the subject which consists in generating artificial cold without the use of ice, it still remains so with me, having nothing new to offer. A considerable acquisition however having been made, since my last Paper “On the best Methods of producing artificial Cold,” by the discovery that a neutral salt, but little known, or attended to, by chemists before, produced extraordinary effects of this kind with ice, it could not fail of attracting my attention.

The facts and results intended to be communicated in this Paper, are founded upon observations made, during the present winter, at the cotton manufactory of Messrs. Philips and Lee at Manchester, where the light obtained by the combustion of the gas from coal is used upon a very large scale; the apparatus for its production and application having been prepared by me at the works of Messrs. Boulton, Watt, and Co. at Soho. The whole of the rooms of this cotton mill, which is, I believe, the most extensive in the United Kingdom, as well as its counting-houses and store-rooms, and the adjacent dwelling-house of Mr. Lee, are lighted with the gas from coal. The total quantity of light used during the hours of burning, has been ascertained, by a comparison of shadows, to be about equal to the light which 2500 mould candles of six in the pound would give; each of the candles, with which the comparison was made consuming at the rate of 4-10ths of an ounce (175 grains ) of tallow per hour.

Production, sustainment and repair technologies for light alloy components in the defence applications account for a significant proportion of Defence Materials Technology Centre (DMTC) activities. Key challenges in this regard include the affordable manufacture and repair & sustainment of Titanium components for new and legacy platforms. The DMTC research program portfolio incorporates collaborative technology development activities between industry and the research sector within a framework of a partnership model that includes input from the Defence customer on likely procurement opportunities for industry, and longer term strategic requirements of Defence. The technological focus is particularly on the benchmarking of strategies, technologies and manufacturing techniques associated with the manufacture of aerospace components via high speed machining. Developing affordable, cost-effective and best of breed machining processes and practices among a broad range of Australian manufacturing organisations is a key goal of the DMTC. This paper describes an initiative of the DMTC focused on developing and optimising engineering capability in metals manufacturing for aerospace applications. Data generated from a range of participating sources conducting machining trials of identical titanium and stainless steel components is compared and contrasted in the context of best practice development.

In the prosecution of my inquiries into the modifications impressed upon light by the various bodies of the animal, the vegetable, and the mineral kingdom, I have had the good fortune to discover several new properties of light, and to establish the laws which regulate the most remarkable of the phenomena. A few of these results have already been laid before the Royal Society ; and from the reception which they have experienced, I have taken the liberty of addressing to you the following paper containing a series of new facts, remark­able for their extreme singularity, and their opposition to almost all our notions of the action of bodies upon the luminous rays. The extraordinary character which these experiments at first assumed, induced me to think that I had overlooked some source of deception ; and it was not till I had performed them under every variety of circumstances, and till they had been repeated, and viewed in the same light by several of my friends, that I prevailed upon myself to bring them under your notice. The splendid exhibition of colours which distinguishes mother of pearl from every other substance, and the succes­sive developement of fresh tints, by every gentle inclination of the plate, have always been ascribed to the lamellated structure of the shell, and have been regarded as a fine proof of Newton's theory of the colours of natural bodies. This explanation I had no disposition to call in question, nor did the general train of my experiments lead me to such an inquiry. In examining the coloured rings which mother of pearl, like the topaz, exhibits by polarised light; and in ascertaining the relation between its refractive power, and the angle at which it gives polarity to the reflected ray, I was under the necessity of grinding and polishing, with the utmost care, various plates of this substance. The developement of new colours, and the extinction of others which took place during these processes, indicated the operation of some unknown and extraordinary cause, and encouraged me to pay the most minute attention to all the phenomena which were presented. The results of this investigation I shall endeavour to explain under the four following heads.

Fig. 1. * This figure is given for the purpose of explaining the mode in which the fibrous disposition of chlorite is effected. The crystallized arrangement which is here so visible is generally observed in those chlorite fibres which occur in transparent quartz. I have never observed it in chalcedony, yet there is little doubt that a similar disposition is equally the cause of the fibrous appearance so common in the specimens which have been figured in the former plates, the chief differences consisting in the smaller size and less perfect crystallization of the chlorite scales. Fig. 2. The crystals of chlorite magnified. Fig. 3. Although in the former plates I figured some specimens which I imagined to be confervæ, I had not then procured any example in which that regularity of structure, which is so conspicuous in some of the plants of this family, could be observed. The present figure exhibits that regularity in a striking manner. Fig. 4. This figure affords a second example of that regular ramification which botanists will immediately recognize as characterizing many of the plants of this tribe; although for the reasons already assigned in the paper, it will be fruitless to attempt to discover the species.

When Mr. Whitby engaged to superintend this most arduous undertaking, Sir Joseph Banks requested him to examine narrowly any caverns he might meet with in the rock, and have the bones, or any other fossil remains that were met with, carefully preserved. Mr. Whitby in compliance with this request, in November 1816, sent up to Sir Joseph Banks a box of fossil bones, which are the subject of the present Paper.

It is proposed in this paper to show in what respects the effects of local attraction, in the above mentioned ships, were conformable to the observations which had been made in preceding voyages; and how far the errors, which were found to take place on different courses, and under different dips of the magnetic needle, corresponded with the rules for calculating corrections, which Captain Flinders had found useful in his own experience, and which he had recommended for a more extensive trial. It may be desirable to premise, that the irregularities here alluded to, are not those accidental disturbances which may be caused by iron placed inadvertently too near the compasses ; but the permanent, and constant effect of the mass of iron contained in a ship, affecting its compasses at all times, and in a greater or less degree, according as its influence is more or less powerful, in comparison to the directive force of the earth's magnetism. That errors have always existed from this cause, may be inferred, from the uncertainty which ex­perience has attached to the results of azimuths observed in ships. The cause, however, appears to have been very long unsuspected, whilst its effects had produced a general impres­sion, that the azimuth compass was in itself an imperfect instrument, and only to be relied on within certain undefined and variable limits.

So deeply is this country in particular interested in whatever may tend to give additional safety to the number of persons, and the immense sums of money employed in commerce, that I trust I shall stand excused for again bringing to the notice of the Royal Society, the subject of the construction of ships. The description of vessels of which I am now about to treat, are those employed in our mercantile service, in the construction of which, the imperfections are such as on a close examination will, I conceive, leave but little doubt that lives and property to an immense amount, must, from time to time, have sacrificed by the present injudicious mode of constructing these ships; and under that impression I have presumed to lay this paper before the Society. And first, as to the principle on which mercantile ships are at present built, and particularly as regards the putting together their ribs or frames, and the arrangement of the materials.

During the course of the year 1814, I had the honour to lay before the Society a paper on the geology of Northumberland and Durham. * It is now my intention to extend that sketch towards the South, taking the Humber and the great north turnpike road for the southern and western boundaries of the district to be described, and the German ocean and the river Tees for the western and northern ones. † It is here proper to remark, that the former are only ideal limits to the formations under consideration; but the latter are real terminations of the rocky strata, a brief account of which will constitute the subject of the following observations. The length of this district is about 60 miles, and its extreme breadth 40; and though the mineral treasures it contains will bear no comparison in respect to number and value with the productions of the country situated to the north and north-west, yet extensive quarries of alum-shale, together with freestone, limestone, chalk, ironstone, and a few thin seams of coal, add in some degree, to the riches of the landed proprietors, and give to many of the poorer inhabitants the means of comfort and support. To begin at the northern extremity of this tract of country, it is necessary to recur to a circumstance mentioned on a former occasion, * viz. that the Tees flows over rocks of fine-grained red and white calcareous sandstones devoid of mica, from a short distance above Croft bridge to the

On the return of the first expedition which sailed for the discovery of a north-west passage, it appeared that from the near approach to the magnetic pole, and the consequent di­-minution of the directive force, the compasses on board had become nearly useless. Some of the azimuth compasses employed on that occasion were of my own invention; I was therefore anxious that the next expedition, which was about to sail under the command of Lieutenant Parry, and which has happily returned with so much honour to those engaged in it, should be furnished with instruments of this description, com­bining as much power and sensibility as possible. It was with this intention alone that I commenced the ex­periments which form the subject of the present paper; but which I should not have deemed sufficiently important to be made public, had I not lately, on resuming the enquiry, been led to some results which appeared of sufficient interest, as well as practical utility, to induce me to lay them before the Royal Society.

On Hampton common and at the top of the Stroudwater vale, towards Cirencester, we have a fine oolite, nearly approaching in texture to Bath stone. Beneath the level of the upper oolite, at Uley great quarry, is a mass of bastard-freestone, differing from Bath stone in the abundance and yellowness of the calcareous matter by which it is cemented, and in being more porous and subject to flake after frost. It contains but few shells. Below this freestone are rubbly beds, consisting of compact sparry masses, irregularly shaped like chalk-flints, very full of shells, and separated from one another by a soft calcareous powder, tinged by iron. The tops of Stinchcombe hill and the other hills in its vicinity that flank the valley of the Severn, exhibit vast heaps of rubble, consisting of bastard-freestone mixed with some fragments of pure white oolite. The organic remains that we here find are three or four species of Anomia, Trigonias daedalea and costata, Ostrea crista-galli, and Porpitae. Beneath this debris, in a quarry on the northern side of Stinchcombe hill, under a high beech-wood, we see a few horizontal beds cropping out from beneath others of the above-described rubbly oolite. These beds are of a warm brown colour, and are rather compact in texture, consisting of a sandy loam (such as here prevails upon the surface) cemented by calcareous spar. These beds are divided into strata of moderate thickness. In the beds themselves but few shells can be distinguished; but their joints are

In the brief account of the transit instrument which I had the honour some time ago of presenting to the Royal Society, I stated the circumstance of the instrument's deviation from the meridian arising from the unequal expansion of its braces; but no instance was then given of the magnitude of such deviation. I now subjoin one. On the morning of Oct. 15, (civil reckoning) after observing the passage of Regulus, the southern shutters were accidentally left open, so that when I returned to observe the inferior culmination of the pole star, the sun was shining on the upper western brace, the object-glass of the instrument being towards the zenith. The effect of this was a retardation of more than 25 seconds in the star's passage, as will thus appear: I now view, with great suspicion, all the observations of the sun's transits, which I observed previously to the detection of that source of inequality which is the subject of the present, and of my former communication.

The object of the present communication is to show, by a series of experiments, that the solar rays possess sensible magnetic properties, which are observable in the vibrations of a magnetised needle exposed to those rays, independently of the effects produced by the heat which they impart. I propose likewise to point out the changes which take place in the intensity of a magnetised needle from changes of temperature, as deducible from the times of its vibration. I have before stated in my paper on the effects of temperature on the intensity of magnetic forces , that, in deducing the terrestrial magnetic intensity by means of the vibrations of a needle, a correction ought to be introduced where the observations have been made at different temperatures. I had not at the time made any experiments by which I could ascertain how far changes in the temperature of a needle would be sensible in the time of its vibration; and the first observations which I made with this view being with a light needle, did not give very decided results: they however led me first to notice the very singular fact, that a magnetic needle comes to rest more quickly when vibrated exposed to the rays of the sun, than when vibrated in the shade. In order to ascertain the effect which changes of temperature have on the times of vibration of a needle, it is necessary to know the temperature of the needle itself during the observations, and I saw no better means of ascertaining this, even approximately, than to vibrate it in the shade and then exposed to the rays of the sun, and to consider the temperature of the needle to be that indicated by a thermometer near to it. On my first doing this, I found, that although I could easily mark the 50th vibration when the needle was shaded, I could not distinguish beyond the 40th when it was exposed. I at the same time found that the time of vibration was slightly diminished at the higher temperature, instead of being increased, as I had reason to expect. As however the needle was not vibrated in the same spot in the two cases, the diminution in the time of vibration and of the arc when it was exposed, might be independent of the change of temperature and of any influence in the solar rays. To avoid any uncertainty arising from difference of disturbing causes in two situations, I placed the compass out of doors, with a screen composed intirely of wood, supported at the height of four feet above it, and by removing which the rays of the sun struck directly on the needle. A thermometer having the bulb near to the compass-box indicated nearly the temperature of the needle. When the shutter was up, so that the needle vibrated in the shade, I could very distinctly note the 100th vibration; but when it was removed and the needle vibrated exposed to the sun's rays, I could not so distinctly mark the 75th. I made use of a needle six inches long, weighing 42.75 grains, and contained in a brass compass-box with a glass cover: the needle was suspended by a fine hair, and commenced vibrating 30° from zero.

The attention of the Board of Longitude having been directed to the state of the Solar Tables used in the construction of the Nautical Almanac, the Astronomer Royal was requested to furnish the Board with a comparison of the computed and observed Right Ascensions of the Sun since the erection of the new transit instrument at Greenwich : and I was desired to examine the discrepancies with a view to the discovery of the errors in the elements of the tables. The papers containing this comparison I received at the beginning of June last; and in the last summer, as soon as other engagements permitted, I undertook the laborious work of examining the discordances. The corrections of the elements determined by these calculations agree in general with those that have been obtained from other observations ; but in one particular, and that an important one, there is a very remarkable difference. The results of such an inquiry will perhaps be acceptable to the Royal Society ; and the singularity of the conclusion which I have mentioned, will make it necessary for me to describe the manner in which I have obtained it.

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In a former paper which the Royal Society has done me the honour to place among its Transactions*, a method of producing intense light is described, the object of which is to render visible distant stations in geodetical operations. At the conclusion of that paper I ventured to suggest that this method might be found useful for other purposes besides that for which it had been contrived; and more especially for the illumination of light-houses. Soon after its publication, I received, through my friend Colonel Colby, a communication from the Trinity House, under whose jurisdiction and manage­ment the greater number of light-houses on the coast of England and Wales are placed, intimating the intention of that Corporation to give the method pro­posed a fair trial, whenever the apparatus should be brought to such a state of perfection as would ensure the steady continuance of the light, while at the same time it admitted of being entrusted with safety to the hands of the ordi­nary attendants. A good deal remained to be accomplished before this degree of simplicity could be considered as attained: nevertheless, the offer of the Cor­poration was prompt and liberal; and, with the assurance that the time and labour devoted to this object would not be vainly and unprofitably expended, I was anxious to undertake the necessary experiments without delay.