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XI. Notices respecting New Books.

An Introduction to Physical Measurements, with Appendices on

Absolute Electrical Measurement, fc. By Prof. F. KOHLRAUSCH. Third English edition, translated from the Seventh German edition, by T. H.WALLER, B.A., B.Sc., and H. R. PROCTER, F.I.C., F.C.S.

London: J. and A. Churchill, 1894. SOME

ME time ago reference was made in these pages (Phil. Mag.

[5] vol. xxxvii. pp. 331, 502) to the fact that the earlier editions of this work had become somewhat out of date by reason of the widening of the scope of physical measurements. Prof. Kohlrausch very rightly pointed out that the fault did not lie on his side, as the latest (seventh) German edition contained a very large amount of new matter. This edition now becomes accessible to us in the form of an English translation.

Prof. Kohlrausch has aimed at giving a tolerably comprehensive list of experiments which may be performed in a physical laboratory, as exercises for students or as parts of a physical research. This wideness of aim necessarily entails a certain amount of brevity of description, and consequently details of apparatus are generally omitted. The book differs in this respect from others of its class, the majority of which are either intended to meet the wants of special students or else have been compiled primarily for use in some particular laboratory: in either case the details referring to construction or arrangement of apparatus are often found inapplicable when the book comes to be used under other conditions. Prof. Kohlrausch has omitted mere lecture-experiments and such as are designed to establish the truth of physical laws: it is assumed in all cases that the experiment is undertaken to determine some physical constant. The omission of the determination of coefficients of absolute expansion of liquids by heat, and the measurement of wave-lengths by the biprism, may be due to this cause, although the former are often required in physical work. A more important defect is the absence of all reference to the measurement of latent heat, either of fusion or vaporization. In connexion with electricity and magnetism the number of experiments which might be described is now so great that a selection becomes necessary, and in the present volume the choice has been on the whole a good one. The only measurement which does not receive attention is that of the mutual induction between a pair of coils, no method being given for its determination. In describing the various forms of galvanometer the D'Arsonval or suspended coil type ought to have been included; and in connexion with Mance's method for the measurement of battery resistance the use of a condenser with the galvanometer (Lodge, Phil. Mag. June 1877) should be referred to. It does not seem to be generally known that satisfactory results can be secured by this simple device. In the appendix on the absolute system of measurements the dimensions of dielectric capacity and magnetic permeability are each given as zero, with the result that the same quantities appear to be of different dimensions according as they are measured in electrostatic or electromagnetic units.

The translators have given a fair rendering of the German text, but unfortunately they have retained nearly all the misprints of the original. This is the more remarkable seeing that a printed list of corrigenda exists, and has been issued with (at any rate, some) copies of the German edition. Out of this list of fifteen misprints only three are corrected in the present translation. Several additional ones have been introduced, the most unfortunate of which is the use of the word “ density” for “specific gravity” on p. 44, just in the place where a distinction is being drawn between the two terms. In the tables at the end of the work a few minor omissions and misprints occur; for example, in Tables 30, 32, and 33 the units of measurement are not stated, while in Tables 22 and 22 (a) C.M.G. is printed for C.G.S. The symbols used by Prof. Kohlrausch have generally been retained, especially in the sections dealing with electricity, where the use of i for currentstrength and w for resistance will scarcely commend itself to English readers. On the other hand, Kohlrausch’s n for refractive index has been replaced by , in accordance with English usage. The volume forms an important addition to the literature of the physical laboratory, and can easily be cleared of such superficial blemishes as have been indicated.

JAMES L. HOWARD.

Watts' Dictionary of Chemistry. Watts' Dictionary of Chemistry ; revised and entirely rewritten.

By M. M. PATTISON Muir, M.A., and H. FORSTER MORLEY, M.A. Assisted by eminent Contributors. In four volumes. Vol. IV.

London : Longmans, Green, & Co., 1894. This fourth and concluding volume of the well-known chemical dictionary brings to a close a standard work of reference of which the first volume appeared in 1888. Altogether we shall not be far wrong in stating that the editors have taken about a decade in revising, rewriting, compiling, and editing the vast amount of material which constitutes the modern science of Chemistry. That they have done their task well has already been acknowledged in noticing the former volumes in the pages of this Magazine. It is with great satisfaction that we are enabled to renew this acknowledgment in the case of the present volume, which extends to 922 pages and contains an Appendix of 34 pages comprising the more noteworthy of the recent discoveries in inorganic chemistry.

A dictionary of science is not an easy work to treat of from a reviewer's point of view. But in this fourth volume there are certain long articles on special subjects by well-known authorities, which form a most valuable feature of the work, and to which attention may

be directed. Thus, instead of the separate articles on electricity, light, heat, &c., which appeared in the old dictionary, we have one comprehensive article on Physical Methods used in Chemistry, which occupies no less than 100 pages and is divided into the fourteen sections :-Capillarity, Crystallographic Methods (references only), Dialysis and Diffusion, Dynamical Methods (references only), Electrical Methods, Freezing-points of Solutions (references only), Optical Methods, Osmotic Pressure (references only), Photographic Methods (references only), Specific Heats of Solids (references only), Thermal Methods, Vapour Pressures of Solutions (references only), Viscosity of Liquids, Volume Changes (references only). In cases where references only are given, it is because the section forms the subject of a special article elsewhere in the work. As a guarantee of soundness of treatment we need only mention the names of the contributors. Thus, Prof. Ostwald is responsible for the section on electrical methods (46 pages), Prof. Hartley writes on optical methods (spectroscopic methods), Mr. George Gladstone the section on refraction and dispersion, and the editor (Mr. Muir) on polariscopic methods. Dr. Capstick contributes the sections on capillarity and viscosity. The section on thermal methods is also written by Mr. Muir. Taking it as a whole this article on Physical Methods is perhaps one of the most valuable in the Dictionary ; with the references and the original communications it constitutes a compact little monograph on Physical Chemistry, and those who have followed the developments of science since the time of the old Watts' Dictionary, cannot but be struck by the vast encroachment of Physics upon Chemistry, to the great advantage of both sciences.

The article on Photographic Chemistry is by Prof. Meldola and is compressed into about 5 pages; Dr. Halliburton contributes 15 pages of most valuable information on Proteids; Mr. O'Sullivan writes on Starch, and also a long article (35 pages) on Sugar, in which the enormous development in this branch of organic chemistry, due chiefly to the researches of Emil Fischer, is very well summarized and set forth. The article on Solutions is divided into two sections--the first, by Prof. Arrhenius, representing the views of those who hold to the physical theory, and the second, by Prof. S. U. Pickering as the representative of the so-called “hydrate” theory. It is interesting to compare the views of the two authors. Arrhenius sets out with the definition:solution is a homogeneous mixture of two or more bodies in the liquid state.” Pickering states :—“The view that bydrates exist in aqueous solutions, and analogous compounds in non-aqueous solutions, is one that has long been held by many chemists; it is only in the last few years, however, that the hydrate or association theory has assumed a precise form, and that definite experimental evidence in support of it has been accumulated.” It is most valuable to have the views of the supporters of the two rival hypotheses thus brought into juxtaposition, and the editors have shown great judgment in inviting contributions from both schools in the present unsettled state of this most important subject.

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Among other special articles attention may be called to that on Specific Volumes by Prof. Thorpe, and that on Terpenes by Prof. Tilden. The latter gives in a space of some 11 pages a very good résumé of our present knowledge of the compounds of this group, and here again one cannot fail to be struck with the great development of chemical science since the publication of the old dictionary. It is chiefly to the work of Wallach, and to the introduction of the conception of the asymmetric carbon atom, that this advancement is due.

The various short articles by the editors do not call for special notice; it is sufficient to state that the standard of excellence has been maintained throughout. It is with the greatest pleasure that we acknowledge the indebtedness of the whole chemical world to the editors of this great work and their coadjutors. The selection of contributors has from the beginning been most judicious, the treatment of the various subjects has been kept well within the bounds of sound knowledge, and the terseness of description has enabled them to compress into the allotted compass of four volumes the vast mass of fact and theory of which the modern science of Chemistry is composed. It is a matter for congratulation that English scientific literature is in possession of such a work. To simply commend it to the notice of chemists is insufficient; we may go so far as to declare that it is absolutely indispensable to every worker in every department of our science.

XII. Proceedings of Learned Societies.

GEOLOGICAL SOCIETY.

[Continued from vol. xxxviii. p. 577.] November 7th, 1894.-Dr. Henry Woodward, F.R.S., President,

in the Chair. THE 'HE following communications were read :

1. • Notes on some recent Sections in the Malvern Hills.' By Prof. A. H. Green, M.A., F.R.S., F.G.S.

The sections described occur on the east side of the Herefordshiro Beacon, and for convenience are named the Warren House Rocks. They are bedded, and have a general north-and-south strike. The great bulk of the rocks are hard, close-grained, and splintery, and are largely altered, and in many cases thickly veined with calcite.

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Details of their structure are given; and the author states that he is inclined to regard them as a group of bedded acid lavas and tuffs, crossed by three bands of dolerite. What little balance of evidence there is seems to be in favour of the intrusive character of the dolerites. No true limestones have been found, and the only very calcareous rock seen is regarded as a rock belonging to the volcanic group which has been largely calcified.

Somewhat similar rocks are found on the southern part of Raggedstone Hill, and a shattered felstone occurs forming an isolated boss south of Chase End Hill.

Several hypotheses present themselves as to the relationship between the Warren House Rocks and the Crystalline Schists. The former may be distinct from the latter, in which case the absence of mechanical deformation would indicate that they are younger. If we consider that the Malvern Schists have been formed out of volcanic rocks by dynamic metamorphism, the Raggedstone Hill rocks may be a portion of the volcanic complex which has undergone only partial transformation, whilst the Warren Hill rocks have altogether escaped metamorphism, the crystalline schists representing its final stages.

2. The Denbighshire Series of South Denbighshire.' By Philip Lake, Esq., M.A., F.G.S.

The area to which this paper chiefly refers is the south-western quarter of the Llangollen basin of Silurian rocks. The beds are bere very little disturbed, and the sequence is readily made out. The following subdivisions are recognized (in descending order) :

Leintwardinensis-slates ; with Monograptus leintwardinensis.
Upper gritty beds; with no fossils known.
Nantglyn flags; with M. colonus, Cardiola, &c.
Moel Ferna slates ; with M. priodon, M. Flemingii.
Pen-y-glog grit.
Pen-y-glog slate ; with M. personatus, M. priodon, Retiolites

Geinitzianus, &c. Farther east the fossiliferous beds of Dinas Brân appear to lie considerably above the Leintwardinensis-slates.

On comparison with other areas it is found that this succession is almost identical with that in the Long Mountain, in North Denbighshire, and in the Lake District. It is also inferred that the Leintwardinensis-slates represent the Leintwardine Flags of Herefordshire, and that the Dinas Brân beds correspond with a part of the Upper Ludlow.

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3. "On some Points in the Geology of the Harlech Area.' By the Rev. J. F. Blake, M.A., F.G.S.

In testing the conclusions arrived at in regard to the Llanberis and Penrhyn area by an examination of that of Harlech, two

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