April 2^, x886] 



NA TURE 



603 



weight." Every element has a molecular symbol and a 

 molecular weight assigned to it. Carbon, for instance, is 

 represented by the molecular symbol C, and by the mole- 

 cular weight 28. Now, on pp. 58 and 59 the reader is 

 given to understand that the molecular weight of a sub- 

 stance is the specific gravity of the gas or vapour multi- 

 plied by 2 (the sp. gr. of hydrogen being taken as unity). 

 On p. 130 it is further stated that carbon in all its forms 

 is non-volatile. How then is the unfortunate student, or, 

 in fact, any one else, to reconcile these statements with 

 that found in the table that the molecular weight of 

 carbon is 28, and what applies to this element appHes of 

 course to most of the others. We may also mention that 

 in another part of the book (p. 160) a molecule of carbon 

 is represented as consisting of twelve atoms. This may 

 of course be a printer's error, but we find the same want 

 of system in symbolic representation throughout the book. 

 We entirely agree with the authors that Inorganic 

 Chemistry should receive more attention at the hands of 

 chemists, but how is it that the authors do so little justice 

 to what has been done in this branch of chemistry? 

 Garzarolli-Thurnlackh's proof of the non-existence of 

 chlorous anhydride is simply ignored, and the statements 

 found in most text-books with reference to this imaginary 

 compound are again reproduced The action of nitric 

 acid on the metals is also represented by the usual text- 

 book equations. 



A good feature in the book is the arrangement of the 

 properties, &c., of the substances described under different 

 headings, which are convenient for ready reference. 



There are many more points to which we might refer 

 if space allowed, but we think we have said enough to 

 indicate that in our opinion, at least, this new manual is 

 not calculated to supply the " want felt, but not yet 

 satisfied." 



OUR BOOK SHELF 



Technical Gas Analysis. By Clemens Winkler, Ph.D. 



Professor in Freiberg. Translated by George Lunge, 



Ph.D. (London : Van Voorst, 1 885.) 

 Prof. Lunge has rendered another service to the 

 world of chemists, both students and practical men, in 

 translating Winkler's small book on " Gas Analysis." We 

 have here a really practical work which a man may use in 

 a works or a teacher or student in a laboratory. 



Winkler's book is scarcely known in this country, and 

 we may venture to say that several, if not most, of the 

 gas apparatus figured and described in this book are also 

 scarcely known. 



The book is decidedly practical, and treats in the first 

 instance of methods of collecting gases ; on measurement 

 of gases ; and on apparatus and methods of analysis. The 

 translator has added a chapter on the nitrometer, and 

 shows how it may be used for more extended analyses 

 than the examination of nitrous vitriol. An appendix of 

 useful tables makes the book a very valuable laboratory 

 companion. 



Lessons in Elementary Cheinis/ry, Inonranic and Or- 

 ga?iic. By Sir Henry E. Roscoe, LL.D,, F.R.S., 

 Professor of Chemistry in the Victoria University, 

 Owens College, Manchester. New Edition. (London: 

 Macmillan and Co., 1886.) 



This favourite text-book is so well known to students 

 of chemistry that, whilst calling attention to the appear- 

 ance of a new edition, we need only remark that the 



author has introduced several changes and additions 

 which bring the book as well up to date as the limits of 

 a work of this size will permit. 



LETTERS TO THE EDITOR 



[ The Editor does not Iiold himself responsible for opinions expressed 

 l>y his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymous communications. 



{.The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible otherwise to insure the appearance even 

 of communications containing intcnsting and novel facts. ] 



New System of Earthquake Observations in Japan 



Owing to the invention of new seismographs by the members 

 of the Seismological Society of Japan, there has been of late a 

 complete change in the system of earthquake observations in 

 this country. The Meteorological Bureau now employs the 

 horizontal pendulum and vertical-motion seismographs of Profs. 

 J. i\[ilne and T. Gray, and of Prof. J. A. Ewing for 

 systeuiatic observation, while the Imperial University of Tokio 

 pulilishes from time to time detailed accounts of particular and 

 more interesting shocks by the use of similar instruments. 

 The e seismographs register on a revolving glass plate or drum 

 automatically started by the earthquake motion, components of 

 horizontal and vertical motions of the earth on a magnified 

 scale, thus producing continuous diagrams, and indicating 

 successive displacement of the ground in conjunction with the 

 time. 



The account of the earthquake of December 28, 1885, the 

 largest shock during the last three months, is here given as a 

 sample of seismic record now issued in this country. The 

 meanings of the terms employed are as follows : a, semi- 

 amplitude of seismic wave ; T, period of complete wave ; V, 



, . . T.Tra 



maxmium velocity m mm. per sec, or r. ; ti, maxinnuu acce- 



■ • y' 



leration ui mm. per sec. per sec. or — . 



At lite Imperial University of Tokio, Japan, at lo/i. 6«. 30^. on 

 December 28, 1885 



Maximum semi-amplitude of horizontal motion a^ ... r8 



Complete period 7\ corresponding to the max. hori- 

 zontal motion ... ... ... ... ... 1-5 



Maximum semi-amplitude of verticil motion 3j ... 0-3 



Complete period T., corresponding to the max. 



vertical motion ... ... ... ... ... o'6 



Direction of the max. horizontal motion E.-W. 



Duration ... ... ... ... .. ... 3m. 30s. 



Remarks. — The motion slowly commenced, not accompanied 

 by quick tremors, as is usually the case. At the 14th second 

 from the commencement a considerable E.-W. motion occurred ; 

 in another second the maximum movement appeared in the same 

 direction, which was followed by smaller shocks during about 

 one minute ; and from thence the oscillations gradually sub- 

 sided. As usual, the particles of the ground did not move to 

 and fro, but traced a curvilinear path, although the E.-W. com- 

 ponents always remained greater than the .S.-N. components. In 

 all, over 130 shocks or complete waves were registered. 



From figures given in the above table, the maximum velocity 

 V and the maximum acceleration a may be calculated, which 

 are, in this case for the horizontal motion, 7'6 mm. per sec. and 

 39 mm. per sec. per sec. respectively. The latter quantity is the 

 measure of the intensity of the earthquake, and may be em- 

 ployed in determining the overthrowing power of body and 

 shattering and other destructive effects produced on buildings. 

 Although the records given by the oscillations of fluids, fissures 

 on walls, rattling of wine-glasses, &c. , might tell something 

 about the nature of earthquakes, and are indeed invaluable in 

 absence of suitable instruments, yet for the absolute measure 

 ments of seismic force the method above cited, I believe, is by 

 far the best that has ever been attempted on this subject. 



I may add in respect to the above earthquake, antl in general, 

 that the vertical motions are always — in our experience — 

 smaller than horizontal ones, and the maxima and minima of 

 these two kinds of motions are not synchronous. I shall have 



