342 



NATURE 



[August 13, 1891 



OUR BOOK SHELF. 



Plane Trigonometry for the Use of Colleges and Schools, 

 With numerous Examples. By I. Todhunter, F.R.S. 

 Revised by R. W. Hogg. (London : Macmillan and 

 Co., 1891.) 

 Todhunter's " Trigonometry " is a very familiar friend 

 of ours, and we have now before us a bundle of letters 

 which we received from the author in 1861 and 1862, in 

 reply to our criticisms and corrections of the early edi- 

 tions. The first edition swarmed with small errata, for 

 the pointing out of which we received warm thanks. It 

 was a good book for some years, on account of the 

 excellent collection of problems, but of late it sadly 

 wanted bringing up to date. Mr. Hogg has done his 

 work well, but possibly he would have produced a better 

 independent book. The first 200 pages have undergone 

 very little change, and we have only noted here and there 

 an interpolated article. Chapter xviii., " Miscellaneous 

 Propositions," contains several novelties (as contrasted 

 with the last edition we have of the original work), such as 

 geometrical proofs of familiar formulae and graphs of 

 the trigonometrical functions. There are numerous 

 important additions in chapters xxi.-xxiv., which bring 

 this part of the work more en rapport with present day 

 requirements, notably Schlomilch's resolution of sin 6 

 into factors, and a too brief account of hyperbolic func- 

 tions. The prime feature is the addition of a very great 

 number of excellent recent exercises in all parts of the 

 subject. The work forms a good school-book, and will 

 meet the requirements of a large number of students. 



Lessons in Astronotny. By C, A. Young, Ph.D., LL.D. 



(Boston, U.S.A., and London : Ginn and Co., 1891.) 

 This is the third of a series of text-books recently pre- 

 pared by Prof. Young for use in schools and colleges of 

 different grades. The two previous ones have already been 

 noticed in Nature (vol. xxxix p. 386, and vol. xli. p. 485). 

 The present work is described on the title page as " a 

 brief introductory course without mathematics, for use in 

 schoo's and seminaries." The three books have much in 

 common, and each one has many good points. We 

 cannot help feeling, however, that the steps between them 

 are too small. Almost exactly the same ground is 

 covered by each, and they differ chiefly in the amount of 

 previous knowledge assumed. But the acquaintance with 

 mathematics required for a thorough comprehension of 

 the " General Astronomy" is by no means great, and even 

 for the "Lessons" a certain knowledge of geometrical 

 principles is essential. If we must needs have three 

 books, the " General Astronomy " contains too little, and 

 the " Lessons" — a book of some 350 pages— contains too 

 much. 



The chief variation calling for notice is in the portion 

 dealing with uranography. This now forms chapter ii., 

 and, with the aid of the maps, forms a fairly complete 

 and easy guide to the constellations. The notes on the 

 legendary mythology of the constellations, which have 

 been added for the benefit of students not acquainted 

 with classical literature, gives this chapter an additional 

 interest. 



The book is brought well up to date, and is a model of 

 good printing. 



Cosmical Evolution : a Nezv Theory of the Mechanism 

 of Nature. By Evan McLennan. (Chicago : Dono- 

 hue, Henneberry, and Co., 1890.) 

 The author states that the essential principle of the new 

 theory is " that every known heavenly body is connected 

 with its neighbouring heavenly bodies by means of real, 

 material bonds, and that every phenomenon of the uni- 

 verse, without exception, is due solely to the action of 

 bodies upon one another through, and by m^ans of, these 

 bonds which join them together" (p. 48). 



NO. J i37, VOL. 44] 



Among the principal evidences in favour of the exist- 

 ence of this material planetary connection is that "we 

 actually see them with the naked eye" in the zodiacal 

 hght and in the streamers of the solar corona. 



The theory is of a very general nature, and includes 

 not only cosmical but terrestrial phenomena, such as 

 aerial and aqueous tides, terrestrial electricity and 

 rnagnetism. The author is of opinion that "the greater 

 tidal wave is due to the sun, and the lesser to the moon " 

 (p. 291). 



The conditions of prelunar and other races of mankind 

 are also discussed (p. 360). The work consists of 399 

 pages. There is no index. 



The Telescope: an Introduction to the Study of the 

 Heavens. By J. W. Williams. (London : Swan 

 Sonnenschein and Co., 1891.) 

 The writer of this book is author of " British Fossils, 

 and where to Seek Them," and " Land and Water 

 Shells, &c." In his preface he quotes with approval 

 the adage, " Ground your knowledge of any special group 

 on a general knowledge of nature as a whole." This 

 is perhaps why he now turns his attention from shells 

 to astronomy. However this may be, the work has been 

 carefully compiled, and is to be recommended as a safe 

 guide. Some of the illustrations are excellent. 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 10 return^ or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Natvrts,. 

 No notice is taken of anonymous communications. ] 



Silver Lodes and Salt Lakes. 



Since the discovery, some five or six years ago, of ihe extra- 

 ordinary Broken Hill lode of silver-bearing ores, the public ex- 

 citement on the subject in this part of the world has been 

 attended with comparatively little scientific interest in regard to 

 the geological features of the argentiferous country and the 

 probable origin of deposits so vast and so remarkable in cha- 

 racter ; yet I believe that an examination of the main topo- 

 graphical and geological features of the eastern parts of South 

 Australia and the western parts of New South Wales will 

 probably throw more light upon the interesting subject of the 

 origin of argentiferous lodes than the study of any other now 

 known part of the globe ; and, as I have had an opportunity of 

 fjoing clo>ely into the matter during a recent visit to Broken 

 Hill, I propose to lay briefly before your readers a few facts 

 which stem to afford presumptive evidence in favour of the sup- 

 position that salt lakes and silver lodes are causally connected. 



An examination of the ores e« situ at Broken Hill, and 

 especially in the portions of the lode which are known as blocks 

 10 and II, reveals the fact that stratification almost exactly 

 similar to that of an ordinary alluvial deposit is practically uni- 

 versal throughout the lode. So obvious has this been from the 

 very beginning of the working, that almost every mining man who 

 has had anything to do with Broken Hill has remarked upon the 

 very obvious fact that the ores are to be ascribed to an aqueous 

 origin. The fissure in which the lode occurs varies from a few 

 feet to seventy or eighty yards in width, and has almost vertical 

 walls. Within these boundaries the stratified deposits of car- 

 bonates and chlorides are intermingled with immense bodies of 

 kaolin and sulphides, with a considerable amount of an interest- 

 ing silicate of zinc also carrying silver and lead. The Barrier 

 District is one of the driest in the whole of this very dry con- 

 tinent, and theie is no river within about seventy or eighty 

 miles. The few intermittent watercourses which exist in the 

 locality do not suggest anything but a dry and arid climate. 

 In fact, the greatest difficulty now met by the mines and 

 by the town of Broken Hill, which contams about 27,000 

 inhabitants, is the scarcity of water, and the doubtful nature 

 of any catching grounds that have been suggested. If, 

 therefore, water was the agency by which the deposits of 



