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Robert William Fogel and G. R. Elton. Which Road to the Past? Two Views of History. New Haven and London: Yale University Press, 1983. Pp. vii, 136. Cloth, $14.95. Review by Stephen Kneeshaw of The School of the Ozarks. Emmanuel LeRoy Ladurie. The Mind and Method of the Historian. Translated by Sian Reynolds and Ben Reynolds. Chicago: University of Chicago Press, 1981. Pp. v, 310. Paper, $9.95. Review by Richard Harvey of Ohio University. John E. O'Connor, ed. American History/ American Television: Interpreting the Video Past. New York: Frederick Ungar Publishing Company, 1983. Pp. 463. Cloth, $17.50; Paper, $8.95. Review by D' Ann Campbell of Indiana University. Foster Rhea Dulles & Melvyn Dubofsky. Labor in America: A History. Arlington Heights, Illinois: Harlan Davidson, Inc., 1984. 4th edition. Pp. ix, 425. Cloth, $25.95. Paper, $15.95. Review by Robert W. Dubay of Bainbridge Junior College. Karen Ordahl Kupperman. Roanoke: The Abandoned Colony. Totowa, New Jersey: Rowman & Allanheld, 1984. Pp. viii, 182. Cloth, $24.95; Paper, $12.50. Review by John T. Reilly of Mount Saint Mary College. Kevin O'Reilly. Critical Thinking in American History: Exploration to Constitution. South Hamilton, Massachusetts: Hamilton-Wenham Regional High School, 1983. Pp. 86. Paper, $2.95. Teacher's Guides: Pp. 180. Paper, $12.95; Kevin O'Reilly. Critical Thinking in American History: New Republic to Civil War. South Hamilton, Massachusetts: Hamilton-Wenham Regional High School, 1984. Pp. 106. Paper, $2.95. Teacher's Guide: Pp. 190. Paper, $12.95. Review by James F. Marran of New Trier Township High School, Winnetka, Illinois. Michael J. Cassity, ed. Chains of Fear: American Race Relations Since Reconstruction. Westport, Connecticut: Greenwood Press, 1984. Pp. xxxv, 253. Cloth, $35.00. Review by Ann W. Ellis of Kennesaw College. L. P. Morris. Eastern Europe Since 1945. London and Exeter, New Hampshire: Heinemann Educational Books, 1984. Pp. 211. Paper, $10.00. Review by Thomas T. Lewis, Mount Senario College. John Marks. Science and the Making of the Modern World. Portsmouth, New Hampshire: Heinemann Educational Books, Inc., 1983. Pp. xii, 507. Paper, $25.00. Review by Howard A. Barnes of Winston-Salem State University. Kenneth G. Alfers, Cecil Larry Pool, William F. Mugleston, eds. American's Second Century: Topical Readings, 1865-Present. Dubuque, Iowa: Kendall/ Hunt Publishing Co., 1984. Pp. viii, 381. Paper, $8.95. Review by Richard D. Schubart of Phillips Exeter Academy. Sam C. Sarkesian. America's Forgotten Wars: The Counterrevoltuionary Past and Lessons for the Future. Westport, Connecticut: Greenwood Press, 1984. Pp. xiv, 265. Cloth, $29.95. Review by Richard Selcer of Mountain View College. Edward Wagenknecht. Daughters of the Covenant: Portraits of Six Jewish Women. Amherst: University of Massachusetts, 1983. Pp. viii, 192. Cloth, $17.50. Review by Abraham D. Kriegel of Memphis State University. Morton Borden. Jews, Turks, and Infidels. Chapel Hill and London: University of North Carolina Press, 1984. Pp. x, 163. Cloth, $17.95. Review by Raymond J. Jirran of Thomas Nelson Community College. Richard Schlatter, ed. Recent Views on British History: Essays on Historical Writing Since 1966. New Brunswick: Rutgers University Press, 1984. Pp. xiii, 524. Cloth, $50.00. Review by Fred R. van Hartesveldt of Fort Valley State College. Simon Hornblower. The Greek World, 479-323 B.C. London and New York: Methuen, 1983. Pp. xi, 354. Cloth, $24.00; Paper, $11.95. Review by Dan Levinson of Thayer Academy, Braintree, Massachusetts. H. R. Kedward. Resistance in Vichy France. New York: Oxford University Press, 1978. Paper edition 1983. Pp. ix, 311. Paper, $13.95. Review by Sanford J. Gutman of the State University of New York at Cortland.

The Microsoft Excel ‘Solver’ tool is a very simple but powerful procedure, even in the hands of the mathematically disadvantaged. It has very good application for quickly fitting experimental flow-curve data to non-Newtonian flow models with any number of parameters, and can cope with data from a number of sources. Examples are given for a range of industrially important examples ranging from standard non-Newtonian liquids, through detergent solutions to gels, pastes, and filled polymer melts, often measured on different viscometers.

A frequent task undertaken by quality-control personnel in typical consumer-goods factories is the measurement of the viscosity of liquid products. The problem often faced in this task is how to strike the correct balance between the complete rheological characterisation of the non-Newtonian properties of the liquid of interest – which requires expensive, sophisticated equipment and can be quite time-consuming – and the dictates of production pressures that demand, as near as possible, an instant decision, and one usually based on a single number. Here we consider the rheological issues that arise in such a debate, which is aimed at finding what adequate characterisation would require.We will investigate the implications of liquids products being non-Newtonian for two of the most commonly encountered viscometers in factory quality laboratories, i.e. the simple ‘dip-in’ rotating spindle viscometer of the Brookfield type (with its different forms and many imitations) and the more sophisticated concentric-cylinder-type device typified by the Haake Rotovisco VT 550 range. Each is capable of giving a single-number answer for viscosity, but the implications of understanding this single number are different in each case, with the dip-in viscometer being in an infinite sea of liquid and the concentric-cylinder situation being narrow gap. We also investigate when the infinite sea of the ‘dip-in’ viscometer is effectively ‘infinite’ and when is a concentric-cylinder geometry really ‘narrow gap’? We will use the power-law model throughout our discussions.

This short article is a summary of a recently published, lengthy review [1] in which the author challenges the often-accepted view that materials have yield stresses, below which no flow takes place. However, following the introduction of the new generation of controlled-stress rheometers it is shown that when careful measurements are made below the supposed ’yield stress‘, flow does actually take place. The argument for the nonexistence of the yield stress as a physical entity now seems insuperable. However, in spite of this, it is nevertheless accepted that an apparent yield stress is a useful mathematical abbreviated description of limited data over a given range of flow conditions. This yield stress parameter can be used effectively for predicting flow, but only within the region of the original measurement that furnished the yield stress.

Process viscometry has many advantages in terms of saving time and gaining more immediate information about a process. However, it can also has disadvantages in terms of compromises that must be made in taking a stream of liquid and passing it through a viscosity-measuring element. The latter operation can be a strong function of flow rate through the instrument, making the measured value variable. The viscometer itself might has been chosen for simplicity of measurement, but which might actually represent a complicated flow pattern in the sense of being a mixture of shear and extensional flow, frequency and acceleration. The best practice in the area of on-line viscometry is reviewed, and the current commercial instruments are compared to this standard. It is concluded that the choice of instrument depends on the pressing need is either for quick information or for reliable information. The Nametre vibrating sphere and the Brookfield concentric-cylinder instruments are highlighted.

The history of commercial viscometry and rheometry over the last thirty years is summarised. In terms of those instruments that have established themselves in a lasting position in the field, we highlight the importance of a sound original idea, good marketing, and constant improvement as technology advances. Instruments in this area fall into three categories: simple, low-cost instruments to measure viscosity or at least an equivalent Newtonian viscosity; multi-speed instruments often able to record data on another display or storage device, and rheometers, i.e. instruments capable of a rotational shearing action, as well as one of the following: oscillation, creep and normal force measurement to give some measure of viscoelasticity. The advances in technology in many areas over the past 30 years have all fuelled the rapid development of instruments that has been nothing short of astonishing. Of especial importance has been the continuous developments of electric motors, and transducers, as well as the increases in speed and memory and reductions in price of digital processors and microprocessors. With this increased computing power perhaps with instruments using complex flow regimes it may be as easy to analyse data as with simple shearing now. There will always be, however, those who want to go to higher frequencies, lower deformations, etc., to meet those challenges of measuring the rheology of materials at the limits.

The flow properties of an emulsion are obviously among some of its more important physical attributes in either technical or aesthetic terms. Hence the ability to measure, adjust and, if possible, predict such properties is very important. The linear viscoelastic properties are first discussed, i.e. frequency-dependent storage and loss moduli and the time-dependent creep modulus. Then the non-linear, steady state properties such as shear viscosity and normal stress differences are covered, the latter being measurable with care, but because they are so small, it is concluded that for all practical purposes normal stresses — and thus overt elastic effects like die swell and the Weissenberg effect — are irrelevant for most emulsions. The basic rheology-determining parameters of an emulsion are considered next: continuous phase rheology and the nature of the drops (size distribution, deformability, internal viscosity, concentration and nature of particle—particle interaction). These are best discussed as they change the parameters of the so-called Krieger—Dougherty microstructure/ viscosity equation. In qualitative terms the rheology of emulsions is well understood, i.e. the effects brought about by various formulation and processing variables that result in a change of dispersed phase volume, size distribution and particle—particle interaction as well as particle deformability. What we do not have, however, is a very good quantitative understanding — at least compared with dispersions of solid particles — because of the lack of good model systems ranging from monodispersed to known and controlled degrees of polydispersity, together with an independent change in particle deformability. Until this happens, emulsion rheology will continue to be the study of multifunctional effects with best guesses at effects found. For instance, we shall not be able easily to distinguish between the effects of particle deformation and particle-size-distribution width.

The design of a two-color two-spot laser velocimeter based on an argon laser and using backscattered light is presented. The prism assembly used in splitting the laser's output beam into 514.5- and 488.0-nm beams, also allows for the rotation of the two spots about a common center, allowing two components of a flow to be measured. The system was tested at ranges of 50, 100, and 150 m, and the results of these tests are presented.

Consideration is given to the reaction to Barnes and Walters’ 4-page ‘The yield stress myth?’ paper published 21 years ago. It has been cited approximately 180 times since then, as either a standard reference for ‘yield stress’ papers, or to disagree with its sentiment that yield stresses do not actually exist, but are a useful approximation. The references that cite the paper are categorized and commented on.

Slip occurs in the flow of two-phase systems because of the displacement of the disperse phase away from solid boundaries. This arises from steric, hydrodynamic, viscoelastic and chemical forces and constraints acting on the disperse phase immediately adjacent to the walls. The enrichment of the boundary near the wall with the continuous (and usually low-viscosity) phase means that any flow of the fluid over the boundary is easier because of the lubrication effect. Because this effect is usually confined to a very narrow layer — with typical thickness of 0.1–10 μm—it so resembles the slip of solids over surfaces that it has historically been given the same terminology. The restoring force for all the forces that cause an increase in concentration is usually osmotic, and this will always limit the effective slip. In dilute systems, concentration gradients can be present over relatively large distances out from walls, giving what might be interpreted on an overall basis as a thick solvent-only layer. However, as the concentration of the system increases, the layer gets thinner and thinner because it is more difficult to create with the large reverse osmotic force present. However, the enormous increase in the bulk viscosity with increase in concentration means that although thinner, the layer becomes, paradoxically, even more important. Slip manifests itself in such a way that viscosity measured in different size geometries gives different answers if calculated the normal way — in particular the apparent viscosity decreases with decrease in geometry size (e.g. tube radius). Also, in single flow curves unexpected lower Newtonian plateaus are sometimes seen, with an apparent yield stress at even lower stresses. Sudden breaks in the flow curve can also be seen. Large particles as the disperse phase (remember flocs are large particles), with a large dependence of viscosity on the concentration of the dispersed phase are the circumstances which can give slip, especially if coupled with smooth walls and small flow dimensions. The effect is usually greatest at low speeds/flow rates. When the viscometer walls and particles carry like electrostatic charges and the continuous phase is electrically conducted, slip can be assumed. In many cases we need to characterise the slip effects seen in viscometers because they will also be seen in flow in smooth pipes and condults in manufacturing plants. This is usually done by relating the wall shear stress to a slip velocity using a power-law relationship. When the bulk flow has also been characterized, the flow in real situations can be calculated. To characterise slip, it is necessary to change the size of the geometry, and the results extrapolated to very large size to extract unambigouos bulk-flow and slip data respectively. A number of mathematical manipulations are necessary to retrieve these data. We can make attempts to eliminate slip by altering the physical or chemical character of the walls. This is usually done physically by roughening or profiling, but in the extreme, a vane can be used. This latter geometry has the advantage of being easy to make and clean. In either case—by extrapolation or elimination—we end up with the bulk flow properties. This is important in situations where we are trying to understand the microstructure/flow interactions.

E. LeRoy Ladurie. The Territory of the Historian. Chicago: University of Chicago Press, 1979. Pp. viii, 345. Cloth, $21.00. Review by J. B. Smallwood, Jr. of North Texas State University. De Lamar Jensen. Renaissance Europe: Age of Recovery and Reconciliation. Lexington, Massachusetts: D.C. Heath and Co., 1981. Pp. xiii, 402. Paper, $10.95; De Lamar Jensen. Reformation Europe: Age of Reform and Revolution. Lexington, Masschusetts: D.C. Heath and Co., 1981. Pp. xii, 468. Paper, $10.95. Review by Sanford Gutman of State University of New York, College at Cortland. Lacey Baldwin Smith, Jean Reeder Smith. The Past Speaks, To 1688: Sources and Problems in English History. Lexington, Massachusetts: D.C. Heath and Company, 1981. Pp. xii, 350. Paper, $8.95; Walter Arnstein. The Past Speaks, Since 1688: Sources and Problems in British History. Lexington, Massachusetts: D.C. Heath and Company, 1981 . Pp. xiv, 427 . Paper, $8.95. Review by John Wilkes of Trinity & All Saints College of Education, Leeds, U.K.. Carol R. Berkin and Clara M. Lovett, eds. Women, War & Revolution. New York: Holmes & Meier, Inc., 1980. Pp. 310. Cloth, $27.50; Paper, $9.75. Review by Barbara L. Tischler of Brooklyn College; SUNY- Empire State College. Walter Nugent. Structures of American Social History. Bloomington, Indiana: Indiana University Press, 1981. Pp. xiii, 206. Cloth, $12.95. Review by Eckard V. Toy, Jr. of the University of Oregon. Peter Shaw. American Patriots and the Rituals of Revolution. Cambridge: Harvard University Press, 1981. Pp. 279. Cloth, $17.50. Review by Raymond Starr of San Diego State University. John A. Schutz. The Dawning of America, 1492-1789. St. Louis: Forum Press, 1981. Pp. 217. Paper, $7.95. Review by Richard Robertson of Alabama Humanities Resource Center. George T. McJimsey. The Dividing and Reuniting of America, 1848-1877. St. Louis: Forum Press, 1981. Pp. 219. Paper, $7.95. Review by Charles F. Bryan Jr. of the University of Tennesse. Elizabeth Frick. Library Research Guide to History: Illustrated Search Strategy and Sources. Ann Arbor, Michigan: Pierian Press, 1980. Pp. x, 81. Cloth, $9.95; Paper, $5.95. Review by Howard A. Barnes of Winston-Salem State University. On Teaching Recent History: An Exchange. Joe P. Dunn of Converse College and William Griffen and J. D. Maricano of SUNY College, Cortland.

Experimental studies of dense suspension rheology as practiced in conventional rheometers cannot reveal the origins of the complex flow behaviour nor even provide consistent data for the development of theory. Applications of particulate computer simulations to dense suspensions are reviewed. These novel alternative “experiments” have the advantages that thermodynamic, structural and other transport data are simultaneously forthcoming and instrumental artifacts eliminated. All the common non-Newtonian flow phenomena characteristic of dense suspensions, together with the various time-dependent manifestations are seen to occur in very simple model fluids in certain density-shear rate-time domains and relate to a steady-state phase diagram. Simulation results could resolve many of the inconsistencies of existing rheometry and point the way to improved design. Furthermore, applications will eventually extend to problems of processing suspensions in industry.

The discharge of electricity from pointed conductors has been the subject of many important investigations, notably by J. J. Thomson, Chattock,Warburg, Zeleny, and others. The effect of moisture on the discharge has recently been studied in detail by Zeleny, who was the first to observe the formation of a coloured deposit on steel needle points when observed under a microscope. He describes this deposit as having a reddish-brown colour, resembling ordinary rust, which is attached to the point in irregular pieces which extend outward some little distance, and finds it produced even in fairly dry air. A marked difference in the volume of the deposit was observed, depending on the direction of the discharge to the point. As anode the amount was much in excess of that produced when the point was made the cathode. As Prof. Zeleny passes over this phenomenon with but a brief mention for the steel' points he used, we considered it of interest to study this deposit more in detail, using pointed conductors of various metals, and to observe what effect the presence of the deposit had on the discharge. It appeared to us probable that the deposit was connected with the presence of moisture in the air surrounding the point, and that it could be eliminated altogether by having absolutely dry air. We have found this to be the case, and in consequence one of the disturbing factors connected with point discharge may be eliminated only by working with air from which every trace of moisture has been removed. Most metals react easily with oxygen in the presence of moisture, but especially when made the anode in an electric circuit. It has been shown by one of us, working with Mr. G. W. Shearer, that the metals aluminium, magnesium, and zinc, form, as the first stage of their oxidation, hydrogen peroxide, when immersed in water containing dissolved air or oxygen. The amount of peroxide formed was observed to be considerably increased when the metal was made an anode. Other metals, such as iron, appear at once to decompose any peroxide produced as fast as it is formed. It seems highly probable that the first three metals form over their surface a protective' film which, in the case of aluminium, is exceedingly resistant. The non-formation of this surface film allows free action between the nydrogen peroxide produced and the metal, resulting in the decomposition of the former and further oxidation of the latter. The formation of the surface film on aluminium has been frequently studied, especially in connection with the asymmetric conductivity of that metal. The readiness with which the surface film may be broken down by the current, when travelling from the metal as cathode, indicates, we think, the incompleteness of the oxidation producing the film.

The primary object of the present series of experiments was that of equipping the McDonald Physics Building of McGill University with a reliable and accurate set of standard cells, and not that of forming the subject of a communication to any scientific paper. In the course of the work, however, several points have come under our notice, which we venture to think may be of interest to others engaged in any investigation requiring the employment or construction of such standards. Among other points, we have devoted special attention to the accurate determination of the temperature-coefficients of various forms of Clark cell; to the construction of cells free from “diffusion-lag” consequent upon change of temperature; and to the investigation of the limits of accuracy attainable with Clark cells under both constant and varying temperature conditions.

The icebergs which infest the North Atlantic have their origin in the glaciers of Greenland. The ice composing them is formed by compression of snow and frost, and in consequence possesses structural characteristics very different from those of ordinary ice, which we may call thermal ice. Glacial ice has been studied a great deal, and the literature on the subject is voluminous.

An experimental study is described which seeks to assess the effect of elasticity on the flow of elastico-viscous liquids as they are made to flow through curved pipes under a pressure gradient. Wherever possible, the experimental results are discussed in the light of existing theoretical predictions and good agreement between theory and experiment for viscous and elastico-viscous liquids is indicated. The general flow pattern for elastico-viscous liquids is shown to be similar to that for Newtonian liquids consisting of two spirals separated by the central plane. Elasticity has a significant effect on the pitch of these spirals. The flow rate in the case of laminar flow and in the transition region between laminar and turbulent flow is significantly enhanced by the presence of elasticity in the liquids, but the opposite is the case in turbulent flow at high Reynolds numbers. Many materials of industrial importance can be classified as elastico-viscous liquids in the sense that they flow under the action of applied stresses and yet have some of the properties usually associated with solids. In technological processes, these elastico-viscous liquids are often pumped through pipes which are usually straight but are sometimes curved. It is therefore of some practical importance to study the behaviour of elastico-viscous liquids as they are made to flow through straight and curved pipes under the action of a pressure gradient. The flow of viscous and elastico-viscous liquids through straight pipes is well documented, but very little consideration appears to have been given to the flow of elastico-viscous liquids through curved pipes. In the present paper, we shall indicate the various interesting features which have arisen from an experimental study of the flow of elastico-viscous liquids through straight and curved pipes of circular cross-section. Our work has been primarily motivated by technological requirements, but it may have applications in other spheres. For example, it may throw light on the flow of blood in the larger capillaries, since it is known that whole blood is non-Newtonian in its behaviour.

In 1902 there were published the results of an extended series of measurements of the capacity for heat of water at different temperatures between 0° and 100°C. The continuous method of calorimetry was employed in the work, the details of which were developed by Prof. H. L. Callendar and myself. A steady electric current was used to heat a steady flow of water through a fine bore tube, bringing about steady temperature conditions in the calorimeter. The energy given in joules per calorie was expressed in terms of the international electric units, and was consequently dependent on the values of the standards used in the measurements. The very greatest possible care was exercised in selecting the standards employed and in making sure that they represented the values assumed for the international electrical units. Previous to the commencement of the investigation of the capacity for heat of water, several years were devoted to a thorough study of the Clark cell as a standard of electromotive force and to the determination of the temperature coefficient of the Clark cell. From a large number of cells suitable examples were selected which were as perfect as could then be obtained. Additional cells were also made at different times and with different materials, in order that those actually used in the investigation could be expressed in terms of the mean of as large a number as possible. In addition, a further investigation of the Weston cell was made, and the mean of all the Clark cells was compared with the mean of all the Weston cells. The value of this ratio was found to be Clark at 15°C. / Weston at 20°C. = 1·40666, which is practically coincident with the value of the ratio found by Jaeger and Lindeck for the cells prepared at that time at the Reichsänstalt. They found Clark at 15°C. / Weston at 20°C. = 1·40665.

In a brief note published in the ‘Physical Review,’ we have described a thermal method of observing the change from stream-line to eddy motion for water flowing through pipes of different diameters. This method we have recently employed in a series of experiments, which we have carried out on a much larger scale than was previously attempted. The method had several points to recommend it for our particular work, the chief one being the simplicity of the experimental arrangements. The object in undertaking this investigation, for which our method was adapted, was in the interest attached to a study of stream-line flow, where every form of initial disturbance was as completely removed from the water as possible.

The unsatisfactory state of our knowledge of the Mechanical Equivalent of Heat and, inseparably connected therewith, of the capacity for heat of water, is the more surprising when we consider the large number of physicists who have devoted their attention to this subject during the century just closed. Since the remarkable pioneer experiments of Count Rumford, undertaken just 100 years ago, to determine the nature of heat, the subject has been advanced step by step by different investigators. Conspicuous among these we may mention Begnault, who gave us the first idea of the mode of the variation of the specific heat of water with temperature, without, however, giving us any knowledge of the mechanical equivalent of heat; Joule, who gave us the first measurements of the mechanical equivalent without attempting to study the thermal unit at different temperatures; Rowtland, who by the remarkable accuracy of his experiments gave us not only a direct determination of the mechanical equivalent, but also the variation of the thermal unit over a limited range. More recently we have the exceedingly careful experiments of Miculescu, of Griffiths, of Schuster and Gannon, and of Reynolds and Moorby. It is evident from only a cursory glance at the work of these and the host of other investigators, that the science of calorimetry must he regarded as incomplete and approximate so long as its fundamental unit remains in doubt. To obtain, as is urgently needed, a complete series of determinations of the capacity for heat of water over the entire range of temperature is manifestly impossible by the older methods of calorimetry. A new method has long been required, more completely free from the influence of extraneous surrounding conditions.

In a letter to NATURE published in the issue of December 1, 1910, I showed by means of microthermograms taken on a trip to Hudson's Straits that an iceberg melting in salt water produces a rise of temperature. The experiments were performed on the Canadian Government steamship Stanley, and indicated that when approaching ice a rise of temperature occurred followed by a rapid fall of temperature a quarter of a mile abeam of the berg.

In a recent paper by Glazebrook, Bousfield, and Smith some doubt has been east on the accuracy of my absolute measurements of the specific heat of water by the continuous-flow calorimeter. It is stated that an error of as much as 6 parts in 10,000 might have occurred in the superheating of the oil-stirred platinurn-silver resistances from which the values of the electric heating current were obtained. On the other band, it is also stated that this error might have been as small as 2.5 parts in 10,000. It was with some surprise that I read this statement, inasmuch as the authors could not have been aware of the rapidity of oil circulation which I used. It has been shown by Osborne Reynolds and others that the heat loss from a surface immersed in a liquid moving in turbulent motion is directly proportional to the velocity of flow. The degree of superheating of a wire immersed in oil will depend then directly on the rate of circulation, bully realising this fact, the resistances which I used were designed by Prof. Callendar and myself to be immersed in oil which could be circulated with great rapidity, These resistances are described in our papers, where the illustration shows approximately to scale the relative sizes of the stirrer and resistances. The paddle was rotated at a high speed by a powerful water motor, and the oil was thrown down with such force that a considerable depression was made in the surface. The oil, thrown sideways, passed up around the bars wires, which were wound loosely on the mica frames. I do not know by what standard Glazebrook, Bousfield, and Smith decide what is "normal stirring" or "very vigorous stirring," but it was evident to me at ones that I must have bad much more rapid circulation than anything used by these authors. In testing the accuracy of my experiments special attention was taken of possible superheating, and tests of stirring were made at the time. The good agreement of the various determinations of the specific heat, made with such different values for the heating current and flow of water, make evident that no large superheating error could have existed without being detected.

IN Canada we have made an extended study of the formation of ground-ice, or anchor-ice as it is called here, and consequently I was interested to see a letter in NATURE of January 30 from Mr. Hampson asking for information as to its origin.

THE application of precise temperature measurements to the determination of the formation and disintegration of ice in the St. Lawrence River suggested to me the possibility of using very delicate electrical thermometers on shipboard to determine the proximity of icebergs. On account of the difficulty of the experiments, and the fact that well-known authorities on navigation (including Lord Kelvin) had reported that temperature measurements were likely to be uncertain, except when very close to a berg, it was some time before I could arrange for the necessary trials.

IN a recent communication to the Physikalische Zeitschrift (No. 18, September) Paschen has described some experiments which indicate that the γ rays from radium supply a large proportion of the total heat emission. It is known that the heating effect of radium when surrounded by an envelope of sufficient thickness to absorb both the α and β rays is about 100 gram calories per hour per gram. Paschen, however, found that if the radium was surrounded by a sufficient amount of lead to absorb completely the γ rays the heating effect was increased 2.26 times. This large heating effect of the γ rays was so unexpected, and of such great importance in connection with the nature of these rays, that we decided to verify this result by an independent method. In Paschen's experiments, the heating effect was determined in a special Bunsen ice calorimeter, in the central tube of which the radium, surrounded by a lead cylinder about 4 cm. in diameter, was placed. In order to correct for the natural melting of the ice mantle a differential method was employed. In our experiments we decided to use a differential air calorimeter, similar to the one described in our previous work on the heating effect of radium and its emanation (Phil. Mag., February). In each flask of the differential air calorimeter there was placed a narrow glass tube, closed at the lower end and extending to about the centre of the flask. The radium bromide weighing 23.7 milligrams was enclosed in a small metal capsule supported by a thread, and was inserted alternately in the glass tubes. The flasks, originally at atmospheric pressure, were immersed in a water bath kept in a constant temperature room, and were connected by a xylene tube which served as a manometer. The heating effect was measured by the movement of the xylene column, observed by a telescope with micrometer oeye-piece, and the scale was calibrated by a small heating coil of approximately the same dimensions as the radium. Two sets of experiments were carried out, in one of which the ends of the glass tubes were inserted in lead cylinders 3 cm. in diameter and 3 cm. high, and in the other with aluminium cylinders of exactly the same dimensions.

Gilbert's (1976) curvilinear model of marital satisfaction and self-disclosure is reinterpreted in terms of an interaction effect between quantity of self-disclosure and quality of self-disclosure. In rural and urban samples of marital couples, regression analyses yielded some support for a significant interaction effect but of a different form than expected. Especially for wives, combinations of low quantity and low quality were found to be extremely detrimental for marital satisfaction. Implications for family life education and marital therapy programs are discussed.

BARNES, HOWARD L., and OLSON, DAVID H. Parent-Adolescent Communication and the Circumplex Model. CHILD DEVELOPMENT, 1985, 56, 438-447. This study tested the relationship between parentadolescent communication and the Circumplex Model of Marital and Family Systems. While most studies of the Circumplex Model have focused on problem families, this study used fathers, mothers, and adolescents from 426 "normal" families. Family scores were developed and used to help describe the type of family system. Because of generational differences in terms of how parents and adolescents perceived their communication, separate analysis was done for each group. It was hypothesized that Balanced families (Circumplex Model) would have more positive parentadolescent communication than Extreme families. This hypothesis was clearly supported for the parents but not for the adolescents. In contrast to the conflicting findings using individual level analysis (parents and adolescents), the findings at the family level using discriminant analysis indicated a linear relationship between parent-adolescent communication and the Circumplex dimensions (cohesion, adaptability) and family satisfaction. Families with good parent-adolescent communication perceived themselves in terms of the Circumplex Model as higher on family cohesion, family adaptability, and family satisfaction.

IT was found by Forbes many years ago that the thermal conductivity of ice was better along the principal axis than at right angles to it. Straneo, in 1897, does not come to any definite conclusion in deciding that such is the case. It is well known, however, that the formation of surface ice by conduction always shows the principal axis of the crystals to be normal to the freezing plane, or, in other words, in the direction of the flux of heat from the underwater. Since ice is a better conductor of heat than water, it is to be expected that if any difference exists in the conductivity in the two directions, the ice crystal would form in such a way as to dissipate the heat more readily.

IN a recent book,1 one of us (H. T. B.) has pointed out that water deprived of trihydrol would be quite useless to living organisms. This suggestion has been supported by experimental results,2 which demonstrate that water rich in trihydrol obtained from melted ice will sustain filaments of the alga Spirogyra in a normal condition for several days, in contrast to filaments maintained under the same external conditions in water from the same source containing a lower proportion of polymerised molecules; in this dihydrol water the protoplasts soon shrink and the filaments become quite limp, due to loss of turgor.