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hydrogen. No one knows better than myself that the fringe of the subject only is touched. When the investigator has the means of examining the general properties of matter under new conditions, surely in our time he does not claim originality for the selection of the order in which he attacks the

many problems ready to hand? The fact is the claims set forward by Prof. Olszewski are fantastic and unfounded.

Professor Olszewski has done good work in the determination of the pressure and temperature relations of the liquid gases, but in future it is to be hoped he will modify his claim for general priority in everything relating to Low Temperature Research.

Royal Institution, 14th Feb. 1895.

XXX. Notices respecting New Books. Select Methods in Chemical Analysis (chiefly Inorganic). Ву

WILLIAM CROOKES, F.R.S. &c. 3rd edition, rewritten and

enlarged. (London : Longmans, Green, & Co., 1894.) THE CHE subject of chemical analysis is capable of being regarded

from two points of view—first as a means of training students in exactness of work, neatness, cleanliness, carefulness, and so forth, and in the next place as a practical branch of science which the working chemist is constantly obliged to resort to in order to ascertain the composition of some kind of matter. This book by Mr. Crookes, which has now reached its third edition, appeals to the latter rather than to the former class of readers. It has in fact from the time of its appearance occupied a unique position among kindred works, and the new edition will be welcomed by working chemists with the same gratitude that its predecessors were received with when the author first enriched our chemical literature with a compilation of such real practical value.

In speaking of the work as a compilation, we have no desire to detract from its merits. To expect the author of a book on chemical analysis to originate all the processes described would be simply absurd, but, although confessedly a compilation, there is one feature that lifts the present work quite above the level of such productions. A quotation from the preface will explain our statement:

“ The author has merely given such methods as have been proved in his own laboratory. Others-possibly no less efficient--bave been passed over because he cannot vouch personally for their value. A main object has been to bring into notice a number of little-known expedients and precautions which prevent mistakes, insure accuracy, or economise time.”

The user of this book therefore may rest assured that all the

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processes described have received the approval of one of the most skilful masters of chemical analysis in this country.

Taking it for granted that the work has, by virtue of its merits, established for itself such a position that any further commendation on the part of a reviewer would be superfluous, we have only to point out now wherein the present edition differs from the former one which was published eight years ago. In order to justify the title of the work and to keep to its spirit, many of the older and now well-known methods of estimation have been omitted. In fact, these methods have passed from the "select” stage, and, having undergone the test of experience, are now embodied in all works on analysis, so that the working chemist may be assumed to know all about them or (what comes to the same thing) where to find them when wanted. Other processes have, we are told, been left out for the opposite reason–because they have not stood the ordeal of experience, but have been supplanted by better ones. The ordinary volumetric processes have also been omitted because there are special works, such as that by Sutton, dealing with this subject. Only in certain cases are titration methods described, and then because of their selectness. For a similar reason the ordinary pyrological methods of analysis no longer find place in the volume, but the reader is referred to special treatises on assaying, of which there are several well-known ones.

The effect of all this expurgation, however, has not been to diminish the size of the book, because a large amount of new matter has been added, partly in the form of new processes which have been discovered since the last edition, but more particularly in the form of descriptions of the electrolytic methods of estimating metals, which have been so thoroughly worked out of late by Dr. Classen. This part of the work, which will be found particularly useful to English chemists, confessedly owes its origin to Classen's book, many of the illustrations of apparatus having been taken from this source. Altogether the volume extends with its index to 718 pages, and is divided into sixteen chapters. Of these the first deals with the alkaline metals; the second with the alkaline earths; the third with the rare earths (on which the author is the chief living authority); the fourth with chromium, vanadium, uranium, tungsten, and molybdenum; the fifth with zinc, aluminium, gallium, and iron; the sixth with manganese, nickel, and cobalt; the seventh with silver, mercury, and copper; the eighth with cadmium, gallium, lead, thallium, indium, bismuth; the ninth with antimony, tin, arsenic, selenium, and tellurium ; the tenth with gold and the platinum metals; the eleventh with sulphur, phosphorus, and nitrogen; the twelfth with the balogens and cyanogen; and the thirteenth with carbon, silicon, and boron. In the fourteenth chapter the electrolytic method and certain special methods of gas-analysis are described. Chapter xv. is devoted to certain miscellaneous processes and what in laboratory terms would be called “practical dodges.” The concluding chapter contains sets of useful tables.

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The general scope of the work will be inferred from the foregoing account of its contents. The classification of the elements may appear somewhat arbitrary, but there are good analytical reasons for adopting this arrangement. The details of description have all the lucidity and exactness which we are accustomed to find in Mr. Crookes' writings. Although nearly a quarter of a century has elapsed since the appearance of the first edition, there is no falling off in power of treatment anywhere manifest in the pages of the present volume, the completion of which is a matter of congratulation both for the veteran author and the chemical world.

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A Few Chapters in Astronomy. By CLAUDIUS KENNEDY, M.A.

(Crown 810, 150 pp., 40 jllustrations. London: Taylor & Francis,

1894.) The idea of this book is a very good one. Its object is to elucidate more fully certain points which are merely touched on or only imperfectly explained in works on Astronomy and Mechanics. In the first Chapter we have an explanation of an optical illusion which is frequently noticed, even by casual observers, but of which the reason is not generally understood. This is the fact that a line drawn at right angles to a line joining the horns of the crescent Moon does not seem to pass through the Sun, as of course it really does, but some distance above it. A similar illusion is seen in the apparent downward curvature of meteor-tracks, and the apparent curvature (in some cases) of a comet's tail when very long, as in the Great Comet of 1882. The second Chapter deals with the effect of the Earth's rotation on moving bodies, such as bodies falling from a height, the flight of migrating birds, &c. The third Chapter explains the effect of the Earth’s rotation on projectiles.

The subject is very fully worked out, and in a very interesting manner. In Chapter IV. an explanation is given of the principle of Foucault's pendulum, a subject which is not sufficiently explained in ordinary text-books on Astronomy, especially with reference to places between the equator and the poles. Chapter V. contains an investigation of the position of high tide considered on dynamical principles-a subject which is very imperfectly dealt with in most works on Astronomy. In Chapter VI. we have a description of various forms of the “ Horizontal Pendulum,” an instrument which is not generally known, and which was devised for the purpose of detecting by direct observation the Moon's differential tidal force. Although sound in theory, this instrument does not seem to be capable

of giving any definite results in practice ; for, as Mr. Kennedy says, “in most cases, at least, a gentle breeze pressing on the side of a house would make the wbole basement floor tilt to leeward through an angle considerably greater than the greatest change in the vertical hy the Moon's tidal force."

Chapters VII. and VIII. deal with the Moon's Variation and

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Parallactic Equality, subjects which are not sufficiently developed in Astronomical treatises. The author clearly explains some points in these lunar irregularities which the student may find a difficulty in thoroughly understanding, and clears up some apparent paradoxes with which the subject is beset.

On the whole, this little work will be found of great assistance to students of mathematical astronomy, and we can strongly recommend it to their attention.

J. E. GORE.

XXXI. Intelligence and Miscellaneous Articles.

AN EXPERIMENT WITH SOLID CARBONIC ACID.

BY PROF. K. PRYTZ.

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NCITED by the interesting account by Prof. Bleekrode (Phil.

Mag. xxxviii. pp. 81-89, 1894) of his experiments with solid carbonic acid, I wish to describe an experiment which I have made. A quantity of solid carbonic acid being compressed in a wooden cylinder, I cut the block of the substance in pieces small enough to be put into a stout glass tube r 1.5 centim. wide. When the tube was filled with the pieces of carbonic acid, it was connected with a manometer M, the cock h being open. On closing the cock the index of the manometer rises slowly until the pressure is as much as 5 atm. The index then stands coinpletely still for a tolerably long time; at the same time we see pieces of carbonic acid sink down on melting: only when the whole is melted, and consequently fills the bottom of the tube, does the index suddenly rise again, and now much faster than before.

When the index has reached 10 atm. the cock is opened a little: the melted carbonic acid then evaporates quickly, the pressure diminishes, the index goes back to 5 atm.: there it suddenly stops again, and is stationary until the carbonic acid is again solid, whereupon it slowly goes back to 1 atm.

The experiment is very instructive. It shows better than any other that I know of the fixity and the identity of the melting and solidifying points: it shows that solid carbonic acid only melts under pressure, and it indicates the great difference between the solid and the liquid carbonic acid in respect of conductivity for heat.

I usually place the glass tube in water; the transparent ice crust then formed shows the cold inside the tube. The Physical Laboratory of the

Polytechnical School at Copenhagen.

THE

LONDON, EDINBURGH, AND DUBLIN

PHILOSOPHICAL MAGAZINE

AND

JOURNAL OF SCIENCE.

[FIFTH SERIES.]

APRIL 1895.

XXXII. On the Passage of an Oscillator Wave-train through

a Plate of Conducting Dielectric. By GEORGE UDNY YULE, Demonstrator in Applied Mathematics, University College, London.

I. Introduction.
II. The Phenomena at the First Surface of the Plate.
III. The Phenomena at the Second Surface of the Plate.
IV. The Intensity of the Transmitted Ray,
V. The Intensity of the Reflected Ray.
VI. Discussion of an Experimental Case and a Correction.
VII. The Numerical Value of some of the previous Results.

Synopsis of Symbols.

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I. Introduction. THE problem treated in these pages was suggested by the

following experimental results, for a fuller account of which I may refer to a previous paper t.

A series of wave-trains generated by an oscillator 0 were allowed to propagate themselves along a double-wire circuit LL/ about 100 metres in length. At the middle of the circuit the wires were run through a jar containing a certain depth AB of distilled water, alcohol, or a very dilute electrolyte.

* Communicated by the Physical Society: read January 11, 1895.

+ Phil. Mag. vol. xxxvi. p. 531, Dec. 1893. Prelim. Paper in the Proc. Roy. Soc. vol. liv. p. 96. A sketch of an approximate theory was given in the Phil. Mag. paper, but several assumptions there made were unjustifiable.

Phil. Mag. S. 5. Vol. 39. No. 239. April 1895. Y

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