Imágenes de páginas
PDF
EPUB

e

The

prepare all the members in the following series, and, with th; exception of Nos. and 10, all of them have been isolated (1) CSI, (2) CsBrIg, (3) CsBrąI, (4) CsCII2, (5) CsClBrI, (6) CsCl2I, (7) CsBrg, (8) CSCIBr2, (9) CsCl, Br, (10) CsCl3. The characteristics of these compounds have been fully studied.The law of elastic lengthening, by J. O. Thompson. author has made an extended and thorough investigation on Hooke's law. The experiments were carried out at the Physical Institute of the University of Strassburg, with the advice and help of Prof. Kohlrausch. They lead to the following conclusions :-(1) The generally accepted law of elastic lengthening, x = aP, according to which the lengthening x is proportional to the stretching weight P is only an approximation. (2) The relation between elastic extension and stretching weight can be expressed by an equation of the following form :

[merged small][merged small][ocr errors][merged small]

(4) The true moduli of elasticity, calculated in this way, may be as much as 16 per cent. larger than those determined in the ordinary way. Consequently it will be necessary to recalculate physical constants which depend on the modulus of elasticity.A method for the quantitative separation of strontium from calcium by the action of amyl alcohol on the nitrates, by P. E. Browning. The relation of melting-point to pressure in case of igneous rock fusion, by C. Barus. From the experiments on diabase the relation of melting-point to pressure at 1200° is Tap = 021; at 1100°, dT/dp=029. And since the probable silicate value of dT dp = '25 at 1170, and as this falls within the margin ('020 to 030) of corresponding data for organic substances such as spermaceti, paraffin, &c., it is inferred that the relation of melting point to pressure, in case of the normal type of fusion, is nearly constant, irrespective of the substance operated upon.-The discovery of Clymenia in the fauna of the Intumescens zone (Naples beds) of Western New York, and its geological significance, by John M. Clarke.-A new meteoric iron from Garrett Co., Maryland, by A. E. Foote. A plate accompanies this paper.-Farrington, Washington Co., Kansas, aerolite, by G. F. Kunz and E. Weinschenk.-The skull of Torosaurus, by O. C. Marsh.

[merged small][ocr errors][merged small][merged small]

The paper is founded upon the study of three embryos of Afteryx australis obtained since the author's former communication on this subject was written.

The youngest (stage E') is intermediate between E and F of the former paper, the next (F') between F and G, the most advanced (G') between G and H.

In E' the characteristic form of the beak has already appeared.

in F' the pollex is unusually large, giving the fore-limb the normal characteristics of an embryo wing.

Several important additions and corrections are made to the former account of the skull, especially with regard to the presphenoid region, the basi-cranial fontanelles, and the relations between the trabecular and para-chordal regions.

The account of the shoulder-girdle is amended. In Apteryx oweni the coracoid region is solid, and no pro-coracoid appears ever to be formed: in A. australis a ligamentous pro-coracoid is present at a comparatively early period (stage F', and perhaps E).

An intermedium is present in the carpus in all three specimens, in addition to the elements previously described.

The brain in stage G' is interesting, as being at what may be called the critical stage; the cerebellum is fully developed, and the optic lobes have attained the maximum proportional size and are lateral in position. In all essential respects the brain of this embryo is typically avian.

Royal Microscopical Society, January 20.-Dr. R. Braithwaite, President, in the chair. The Society adjourned after passing a vote of sympathy and condolence to His Royal Highness the Prince of Wales (Patron of the Society) on the sad loss he had sustained.-This being the annual meeting, the President's address, which was to have been read, was therefore postponed till the next meeting, February 17.

EDINBURGH.

Royal Society, January 4.-Prof. Sir W. Turner, VicePresident, in the chair.-Dr. Noel Paton read a paper on the action of the auriculo-ventricular valves. It has hitherto been supposed that, when these valves close, the two flaps are floated up by the fluid, and, partially overlapping, prevent the passage of the fluid by being pressed against each other. Thus it has been supposed that, when closed, the upper surface of one flap presses against the under surface of the other. Dr. Paton has found, by direct experiment, that the flaps remain, on the whole, in a pendant position, the upper surfaces of the two being pressed together.-Mr. John Aitken read the second part of a paper on the number of dust particles in the atmosphere of certain places in Great Britain and on the Continent, with remarks on the relation between the amount of dust and meteorological phenomena.-Dr. Thomas Muir read a paper on a theorem regarding a series of convergents to the roots of a number. The investigation was suggested by some work of the late Dr. Sang. The series does not converge rapidly, and so cannot be of great practical use.-Mr. Malcolm Laurie read a paper on the development of the lung-books of Scorpio, and the relation of the lung-books to the gills of aquatic forms. He was led to investigate this subject by observations made on the allied fossil forms described in his paper read at the previous meeting of the Society. He concludes that the lung-books are not formed by a process of invagination, as is usually supposed to be the case. He considers that the cavities are formed by the growth of a protecting plate which finally adheres to the body.

SYDNEY.

Royal Society of New South Wales, November 4, 1891.-H. C. Russell, F.R.S., President, in the chair.—The following papers were read :-Notes on Artesian water in New South Wales, by Prof. David.-On the constitution of the sugar series, by W. M. Hamlet.

December 2.-H. C. Russell, F.R.S., President, in the chair. The following papers were read:-On kaolinite from the Hawkesbury sandstone, by H. G. Smith.-Notes on some New South Wales minerals (Note No. 6), by Prof. Liversidge, F.R.S.-Notes on the rate of growth of some Australian trees, by H. C. Russell, F. R.S.-Some folk-songs and myths from Samoa, translated by the Rev. G. Pratt, with introductions and notes, by Dr. John Fraser.

PARIS.

Academy of Sciences, January 18.-M. Duchartre in the chair. -Obituary notice on the late Sir George Biddell Airy, by M. Faye.-On the mass of the atmosphere, by M. Mascart. It is shown that the determination of the mass of the atmosphere by observations of the pressures at the surface is open to serious objections, and involves a notable error. The mass, calculated by means of the formule developed by M. Mascart, is onesixth greater than that usually obtained. The quantity of air situated at a height of 64 kilometres is 1/700 of the total mass. Particles of ice and water are suspended at this height, although the air is so rarefied. It is therefore presumed that the density does not diminish uniformly with increase of height above sealevel, but decreases more slowly in high than in low strata. [On this point see a note in NATURE, p. 259.]-New note on the resistance and small deformations of helical springs, by M. H. Resal.-On solar statistics for 1891, by M. Rodolf Wolf. (See Our Astronomical Column.)-Observations of Wolf's periodic comet, made in 1891 with the great equatorial of Bordeaux Observatory, by MM. G. Rayet. L. Picart, and Courty. Observations of position are given, extending from June 27 to December 27.— On integrals of differential equations of the first order, possessing a limited number of values, by M. P. Painlevé.-On an arithmetical theorem of M. Poincaré's, by M. Victor Stanievitch.-On organic compounds as solvents for salts, by M. A. Etard.Action of carbon monoxide on iron and manganese, by M.

Guntz. Pure finely divided manganese, obtained by heating an amalgam formed electrolytically, at 400° completely absorbs pure carbon monoxide as follows:-Mn + CO = MnO + C. The reaction is probably the same in the case of iron. This explains the facility with which C is taken up by iron in the blast furnace. The spongy iron reduces CO, and finely divided C is deposited in contact with the FeO formed; at a higher temperature the FeO is reduced by CO, when the metallic Fe readily takes up the finely divided C intimately mixed with it.— Action of carbon on sodium sulphate, in presence of silica, by M. Scheurer-Kestne".-Lithium nitride, by M. I. Ouvrard (See Notes.) - Action of phosphorus pentachloride on ethyl oxalate, by M. Ad. Fauconnier (See Noes) On the thermal value of the substitution by sodium in the two alcoholic hydroxyl groups of glycol, by M. de Forerand. An isomeride of camphor, by M. Ph. Barlier -The fixation of iodine by starch, by M. E. Rouvier -The rotutory power of silks of different origin, by M. Léo Vignon.-Action of boric acid on germination, by M. J. Morel.-Contribution to the embryogeny of Smicra clasipes, by M. L. F. Henneguy,-On some new Coccidia, parasites of fishes, by M. P. Thélohan. -On the prevention of hiccough by pressure on the phrenic nerve, by M. Leloir. Five years ago the author was consulted by a girl twelve years of age who hiccoughed every half-minute. She was thus prevented from sleeping, or masticating her food, and her life was despaired of. Anti-spasmodic prescriptions were tried in vain. After pressing the left phrenic nerve, however, for about three minutes, the hiccoughing disappeared. The method has since been successful in many other cases-On the muciferous apparatus of Laminaria, by M. Léon Guignard.-On the dorsal insertion of the ovules of Angiosperms, by M. Gustave Chauveaud.-On chloride of sodium in plants, by M. Pierre Lesage. It appears that when Lepidium sativum and Raphanus sativus are watered with a solution of sodium chloride the elements of this salt are found in these plants, consequently a certain proportion of each is absorbed by the plants. Observation of a lunar corona on January 14, 1892, by M. Chapel.

BERLIN.

Physical Society, January 8.-Prof. Kundt, President, in the chair.-Dr. Kurlbaum described a surface-bolometer which he had constructed in conjunction with Dr. Lummer. It is cut out of platinum foil whose thickness is 0.012 mm., and possesses the great advantage of very rapidly coming to rest. It is a trustworthy instrument for the measurement of the differences in luminosity of two sources of light.-Dr. Pringsheim described a lengthy series of experiments made in order to determine whether the emission of light by gases is the outcome of mere elevation of temperature, or whether electrical or chemical processes play a necessary part in their incandescence. Sodium vapours were found to yield their characteristic spectral lines and absorption spectra, when passed through a highly heated porcelain tube, only in the case where chemical processes (of reduction) could be ascertained to take place inside the tube. In the absence of these reduction processes, both the emission and absorption of light by the sodium vapours were wanting. The experiments further showed that Kirchoff's law holds good not only for the emission of light resulting from a rise of temperature, but also for that which results from chemical processes, since in all cases the emission spectrum corresponded absolutely to the absorption spectrum.

He

Meteorological Society, January 12.-Prof. Schwalbe, President, in the chair.-Dr. Sprung exhibited his improved sliding-weight balance, demonstrated its mode of action and extreme sensitiveness, and explained its use in the registration of changes of atmospheric pressure, temperature, and humidity. -Prof. Boernstein spoke of a case of extraordinarily rapid evaporation from both the surface of his body and his clothing, which he had recently observed while on a glacier. expressed his belief that the evaporation was due to the lesser tension of aqueous vapour, for any given temperature, over a surface of ice as compared with its tension, at the same temperature, over a surface of water. Dr. Assmann put forward the view that the phenomenon was due to the extreme and sudden dryness of the air often observed in elevated regions, and to the powerful effect of solar radiation.-Dr. Andries read a passage from Virgil's "Eneid" which contains a most clear description of a cyclone.

Physiological Society, January 15.-Prof. du Bois Reymond, President, in the chair.-Dr. Max Levy described his experiments on the influence of blood-supply to the skin on the secretion of sweat as seen in the paw of the cat. He found that blood only supplies the material necessary for the secretion. Secretion can be obtained even after complete occlusion of the blood-vessels supplying the glands. After anæmia lasting for 35 minutes the sweat-glands are paralyzed, but can recover their functional activity even after having been deprived of blood for five hours.-Dr. Th. Weyl gave an account of the results of his experiments on animals (pigeons and fowls) rendered immune to anthrax. When anthrax spores were introduced on a silk thread under the skin of these animals, the spores retained their full activity at the end of one day's sojourn under the skin. If kept there for a longer period, they lost some of their virulence, and were found to have become quite harmless at the end of six days in the pigeon, and three or more in the fowl.

Erratum. In the report of the Meteorological Society for December 1, 1891 (see NATURE, vol. xlv. p. 168) for "maximum and minimum thermometer" read sling thermometer.'

BOOKS, PAMPHLETS, and SERIALS RECEIVED.

BOOKS.-Cooley's Cyclopædia of Practical Receipts, 2 vols.. 7th edition; W. North (Churchill) -Manual of Chemical Technology: . von Wagner. translated and edited by W. Crookes (Churchill). The Human Mind. 2 vols. J. Sully (Longmans).-The Rainfall of Jamaica: M. Hall (Stanford). -The Horse: W. H. Flower (Kegan Paul).

PAMPHLETS.-A New Departure in Astronomy: E. H. (Chapman and Hall). Hand-book on Viticulture for Victoria (Melbourne, Brain).-Royal Commission on Vegetable Products: I. Ensilage; II. Perfume Plants and Essential Oils (Melbourne, Brain).-Report upon the Condit.on and Progress of the U.S. National Museum during the year ending June 30, 1889: G. B. Go de (Washington).-List of Institutions and Foreign and Domestic Librar.es to which it is desired to send future Publications of the National Museum (Washington).-Te Pito te Henua, or Easter Island: W. J Thomson (Washington). -Ahoriginal Skin Dressing: O. T. Mason (Washington) -The Development of the American Rail and Track, as illustrated by the Collection in the U.S. National Museum: J. E. Watkins (Washington).— Preliminary Hand book of the Department of Geology of the U S. National Museum G. P. Merrill (Washington)-Les Odeurs: M. C. Henry (Pans, Hermann).

SERIALS.-Zeitschrift für Wissenschaftliche Zoologie, liii. Band, 3 Heft (Williams and Norgate).-Morphologisches Jahrbuch, xviii. Band, r Heft (Williams and Norgate).-Bulletin of the Buffalo Society of Natural Sciences, vol. v. No. 3 (Buffalo).-Records of the Geological Survey of India, vol. xxiv. Part 4, 1891 (Calcutta).

[blocks in formation]

THURSDAY, FEBRUARY 4, 1892.

CARPENTER BY DALLINGER.

The Microscope and its Revelations. By the late William B. Carpenter, C.B. M.D., F.R.S. Seventh Edition, by the Rev. W. H. Dallinger, LL.D., F.R.S. (London: J. and A. Churchill, 1891.)

THE earlier editions of Dr. Carpenter's " Microscope" had a satisfactory basis. They formed an excellent guide to the use of the instrument, in days when microscopic technique was far less elaborated than it is now, written by an enthusiastic and experienced worker. Dr. Carpenter told us about the theory of the microscope and the different kinds of stages, rack-works, and objectives which he himself had seen and tried ; and then gave a somewhat casual and purely personal account of different animal, vegetable, and mineral structures which had been investigated with the microscope, and had especially excited his interest and attention. The book was valuable because it contained the advice and judgment of a great authority, and original observations upon a heterogeneous assemblage of objects by a highly competent naturalist. The later editions of the book, even in Dr. Carpenter's hands, lost a good deal of the original character of the work. New matter of all kinds was fitted in, until the volume became very bulky. Still, the selection of material was made by one man, and the work might be regarded as his note-book, his conception of what was most interesting and instructive in the wide field of microscopic research. An edition of such a book by other hands after the death of the original author is not likely to be a real success, though it may justify a publisher's commercial foresight. Dr. Carpenter's name is a good one to trade with ; but as a matter of fact there | is not much of Dr. Carpenter in the present work, and what there is has only impeded the naturalists who have assisted Dr. Dallinger in elaborating its contents. The result is very confusing: the reader often is at a loss to know whether a statement is one surviving from Dr. Carpenter himself or is introduced by the new editor.

The book really consists of five treatises compressed into a single volume, no one of which excepting the first is by any means complete. These treatises are: (1) on the theory of microscopical optics, and the history and present development of the compound microscope and accessory instruments; (2) on microscopic technique ; 3) on the vegetable kingdom and vegetable histology; (4) on the animal kingdom and animal histology; (5) on the microscopic structure of minerals and rocks.

The first of these treatises is a new and original work by Dr. Dallinger, and occupies five chapters. It contains a valuable exposition of the theory of modern objectives, and some interesting records of ancient microscopes. The statements on p. 209, as to the introduction of the Hartnack model and objectives into this country, and the motives which led to it, are entirely erroneous. I had a large share in that innovation; and I have no hesitation in stating that what led to the importation of German and French microscopes direct from their makers was the simple fact that one obtained an efficient instrument for about one-fourth of the price exacted at that time by

English makers for an instrument of no greater practical value; whilst it was also the fact that English dealers (not the great makers) were in the habit of selling inferior Continental objectives (rejected by their makers) as their own "make," at higher prices than would suffice to purchase first-rate glasses from the Continental firms. The result of the diversion of English purchasers to Continental stands and objectives was the simplification of English models, and an enormous reduction in the price of English-made objectives.

The treatise on section-cutting, mounting, use of reagents, &c., is necessarily short, and lacks that completeness and authority which can alone make a laboratory guide really useful. But the chapter on practical microscopy is a really valuable one, giving the matured conclusions of the editor as to the true methods of getting the best possible performance from the instrument. The English school of microscopists is unrivalled in the services which it has rendered to the development of the microscope as an instrument of precision, and in the cultivation of the art of obtaining from it the most perfect optical results by skilful management of illumination, &c., as also of rightly judging and correcting those results. The high eulogy passed on the Royal Microscopical Society (p. 340), in view of its services in thisfield, is amply warranted. It is, however, to be regretted that the name of the late Dr. Royston Pigott, F.R.S., is omitted from the history here given of the improvements in condensers, objectives, and eye-pieces. His valuable contributions to the subject were rejected by the Society in 1870, and published in the Quarterly Journal of Microscopical Science at that period.

The last three treatises are what give the book itsstrange and almost incomprehensible character. There can be no doubt that Prof. Bell would have written an excellent original treatise on microscopic animals, and Mr. Bennett an equally valuable one on microscopic plants; but they have not been asked to do this. They and others, and the editor himself, have contributed fragments which are mixed up with fragments of the original Carpenter in inextricable confusion.

The "Author," with his capital A, appears as of old,. but he will now receive credit for opinions he never held, and would probably have rejected. The present editor is, however, careful to take responsibility himself for a very remarkable statement-namely, that the saprophytic Monadinæ (such as Monas Dallingeri of Sav. Kent and others)

[ocr errors]

'possess features that ally them to the vegetable series, . and indicate affinities with certain Nostocaceæ and the Bacteria; while a leaning to the Mycetozoa [already classed by our editor among Fungi!] and the chlorophyllaceous Algæ, and even some forms of Fungi, is quite apparent to the careful student."

It is somewhat startling at the present day to come across conceptions of this kind-groups "leaning" this way and that, with remote affinities to half-a-dozen incompatible ancestries. One would like to know in plain English whether Dr. Dallinger considers that the Monadinæ have descended from Nostocaceæ, or from Mycetozoa, or from green Algæ, or any of the latter from any of the former, or all from a common ancestor; and. what grounds he has for his view as to their genealogy.

Many of the old topics enlarged upon by Carpenter are treated with increased amplitude in the present edition. Excellent plates (some of them coloured) illustrate the Desmids, the Diatoms (the old crux of the sculpturing of the valves is more than ever to the fore), the Monads, the Rotifers, and the Foraminifera. Three coloured plates of the structure of Acari are introduced; they are very interesting, but surely out of proportion in a work on the microscope where no adequate illustrations of the Ciliate Infusoria are given, and where the account of the phenomena of conjugation in that class is far from being up to date both as to statement and illustration.

I do not wish to speak unkindly of an old friend, even when rigged out in such a strangely variegated new set of clothes as are those furnished to "The Microscope " in its seventh edition. There is a great deal of very interesting matter; there are numbers of excellent woodcuts and plates in the book, some old and a great many new one thousand in all. The defect of all the earlier editions remains in the present-namely, that whilst you may find several pages, plates, and figures about one subject connected with microscopy, you will find only three lines or nothing at all about another. So long as Dr. Carpenter wrote successive additions to the book, one understood why some subjects should be treated fully and others passed over, and at any rate one knew who was responsible for any statement or omission. Now the book has (so far as its second half is concerned) lost its authoritative character, and is more than ever a patchwork of paragraphs on arbitrarily selected subjects, the responsibility for which is divided in some mysterious way between the editor (who, of course, does not claim to be another Carpenter), and certain Fellows of the Royal Microscopical Society.

I should wish, on the other hand, to express the opinion that the first half of the book (which alone really deals with the microscope and the art of microscopy, and is not by Dr. Carpenter, but entirely new-by Dr. Dallinger) is a work of high scientific value-by far the best on the subject and one which every worker with the microscope should thoroughly study and take to E. RAY LANKESTER.

heart.

ELEMENTARY THERMODYNAMICS.

Elementary Thermodynamics. By J. Parker, M.A. (Cambridge University Press, 1891.)

IN,

Na six-lined note, which does duty as preface, the author of Elementary Thermodynamics" tells the beginner what to omit. From a beginner's stand-point the book must therefore be judged. A first glance will probably startle the reader into exclaiming, What can Kepler's laws have to do with Carnot's principle? Fortunately, however, the sections containing Kepler's laws, and much other apparently irrelevant matter, are those the beginner is advised not to read. With the mere remark that all this is preliminary to an elementary exposition of Darwin's calculations in tidal friction, it will best serve all purposes to confine the attention strictly to things thermodynamic. The most important chapters, alike from the teacher's and pupil's points of

view, are the first and third, dealing with the foundations of the science.

The first chapter is headed "The Conservation of Energy." It develops in mathematical form the general differential equation of energy, but is lamentably feeble in the physical or experimental side. True, there is a brief discussion of some of Joule's experiments; but we venture to think it would require a greater than Joule to find that a calorie was equivalent to 41,539,759'8 ergs! A little further on, the latent heat of ice under a pressure of one atmosphere is given as 79:25 calories, or 3,292,025,964 ergs!! Surely it "was the most unkindest cut of all" thus to spurn the o15. The truth taught here is, that ten-place logarithms do bare justice to "Parkerian" reductions.

A novelty of treatment is the division of forces into contact-forces and ether-forces. To Prof. Lodge is ascribed the doubtful honour of having suggested this treatment. Contact-forces, we are told, exist between particles in contact; while "the principal ether-forces in Nature which do work, in addition to gravitation and radiation forces, are those which give rise to chemical, physical, electric, and magnetic actions." It is not easy to see the exact meaning of the word "physical" in this definition. If it includes elasticity, cohesion, adhesion, and capillarity, why should pressure, impact, and frictional effects be excluded? Is there, indeed, any evidence of the existence of contact-forces (in Mr. Parker's sense) between particles? To our gross senses, visible masses seem to get into contact with each other; but, when once we introduce an ether as the vera causa of all actions between bodies not in apparent contact, we are compelled to regard this ether as an ocean in which matter is an archipelago of particles or a swarm of maelstroms. How, then, can "contact-forces" exist at all, since ether must intervene between particle and particle? In any case an elementary text-book is hardly the place to introduce crude ethereal speculations.

Chapter iii. is devoted to "Carnot's Principle,” and these two most significant words form head-lines to 136 pages of a book that just tops the 400. This is good. Nevertheless, the "principle" itself, so far as we can discover, is never once explicitly stated. The chapter opens with a brief historic sketch, in which we are told that Clapeyron brought Carnot's work "prominently " forward in 1834. Yet it was not till fourteen or fifteen years later that Thomson discovered to the scientific world the greatness of Carnot, and clearly pointed out the necessity for modifying Carnot's reasoning so as to bring it into accord with the true theory of heat. From Thomson's second paper (1849) Clausius dates his inspiration. Of all this Mr. Parker says nothing, nor does he seem to be aware that Thomson, two years before Clausius and Rankine published anything, pointed out how Carnot's principle led to the conception of an absolute scale of temperature. Moreover, there can be no question that Thomson first gave an unexceptionable enunciation of the "axiom" underlying Carnot's principle. Such particulars are probably of no interest to an author who defines "the very important axiom . substantially due to Carnot" in language which may be thus paraphrased: No mechanical work can be gained from a cycle of operations imposed upon a system in

thermal communication with two bodies only which are at the same temperature. As a basis for the second law, is not this like Samson shorn of his locks?

But in the really important demonstrations Mr. Parker uses, as a logical equivalent of this, an axiom which again is nowhere given explicitly, but may be thus enunciated: During a complete cycle, in which the working substance is in thermal communication with two bodies each at a constant and uniform temperature, it is impossible for a positive quantity of heat to be absorbed from the one and no heat whatever to be exchanged with the other body. The general truth of this "axiom" will be admitted rather because it agrees with Carnot's principle than because of any inherent merit it may itself possess. An axiom must appeal to experience at bottom; and if one had striven to evolve the said axiom in the most unaxiomatic guise attainable, one could hardly have succeeded better. Sad, indeed, his lot whose introduction to Carnot's principle is through such tortuous paths!

But the impression gathered from a careful consideration of Section 49 is that the second implied form must be regarded as simply another statement of the first implied form of "Carnot's axiom." Take, for example, the following argument:

"The quantities of heat absorbed by the system from the two bodies A, B [each at a constant and uniform temperature] during any complete cycle cannot both be positive. For we could then, by expending work in friction, cause the system to undergo a cycle of operations in which a positive quantity of heat was absorbed from one of the bodies A, B, and no heat at all received from or parted with to the other. In other words, we should be able to take heat from a body whose temperature was uniform and constant, and transform it into work without the presence of any other body of different temperature, contrary to Carnot's axiom."

Little good would be served by criticizing these statements at length, which seem to contain at least as many assumptions as sentences. It would be interesting to know what becomes of the work spent in friction, so arbitrarily introduced, and so cunningly disregarded. After all, however, although the second implied form of "Carnot's axiom" may be generally true, it certainly is not so in the particular case in which the one body is at absolute zero. This is quite as conceivable a contingency as the realization of the assumed thermal conditions of the bodies A and B.

After having, by a perfect volley of reductiones ad absurdum, reduced all reversible cycles, working between the same temperatures, to the same efficiency, Mr. Parker introduces Thomson's absolute scale of temperature in 0 . the usual form la

Then should come (since it has Ꮎ not come earlier) the proof that the reversible cycle has more efficiency than any other conceivable cycle. But all we find is this sentence :

"It will be easily seen that, if the irreversible cycle be non-frictional, qalq will be equal to 0/0, and that in all other cases it will be less."

"It will be easily seen" is easily said, and throws the burden of the proof upon the intelligence of the learnerthe proof of what is the kernel of the whole of thermodynamics. And this is teaching!

It

We are firmly convinced that after reading this third chapter the average student will have the haziest ideas of what reversibility means, will be utterly at a loss to know what Carnot's principle really is, and will look upon the "conception of entropy as a phrase to conjure by. It is with decided feelings of relief that we pass on to chapter iv., "Applications of Carnot's Principle." may be well to remark here that chapter ii., "On Perfect Gases," discusses the simpler thermodynamic properties of the ideal gas obeying Boyle's and Charles's laws. The experimental truth established by Joule, that the heat absorbed by such a gas is equal to the work done by it during the expansion, is made the basis of the whole inquiry. In both these chapters the ground covered is familiar. For example, Thomson and Joule's experimental determination of the absolute zero of temperature is given with commendable fullness. Critical points, latent heats of saturated vapour, and certain aspects of solution and capillarity are all treated in due order, and with sufficient fullness of numerical detail to make them thoroughly intelligible. In the fifth and sixth chapters, again, we are introduced to the thermodynamic potential. We are not aware that the general energy methods of Massieu and Helmholtz have ever before been presented in connected form to English readers. This Mr. Parker has done, and has deservedly earned our tribute of praise. Anyone who is familiar only with the earlier methods by which the founders of the modern theory grappled with the subject, will find these two last chapters, and especially chapter vi., particularly interesting.

The author is not, however, to our mind so happy in his account of Gibbs's thermodynamic surface as, from the tenor of his introductory remarks, we had expected him to be. After animadverting upon "the very brief notice in Maxwell's 'Theory of Heat"" of "this beautiful geometrical construction . . . which does not seem to have obtained the attention it appears to deserve," Mr. Parker proceeds presumably to give it this attention. But what do we find? Five pages of not very lucid description as against Maxwell's eleven and a half. Perhaps, however, this is of small consequence; for, beautiful though it be as a bit of geometry, the thermodynamic surface, even in concrete form, is of doubtful efficiency in the presentation of thermodynamic truth..

Mr. Parker's book possesses not a few merits, but is marred as an educational work by many faults, chief among which is the tangled presentation of the second law. It is hard, indeed, to get up much enthusiasm for an author who speaks of the speed at which a body cools, who casts a slur upon British meteorology by declaring that the Centigrade is "the only thermometer now used for scientific purposes," and who gives no less than three distinct and irreconcilable estimates of the sun's radiation in as many consecutive pages. The loosely expressed but familiar axiom that "heat cannot flow of itself" up a temperature grade is referred to as an important consequence of Thomson's definition of absolute temperature; and of the Maxwell "Demon," and all that therein is, there is not even the suggestion of a hint.

The book ends with an appendix of physical constants compiled from various sources. Otherwise, its usefulness is sadly diminished by lack of an index or even table of C. G. K.

contents.

« AnteriorContinuar »