March 28, 1895J 



NA TURE 



509 



within the grasp of busy medical practitioners. With 

 this object graphic formulae are profusely employed, so 

 that "a glance will lay bare to the eye of the novice the 

 whole details of the constitution of the most complicated 

 compounds," and the practical preparation of the com- 

 pounds has been generally omitted " because the much 

 tried patience of medical men need not be burdened 

 with things chiefly of interest to the chemist." With 

 these exceptions a large proportion of organic chemistry 

 is very fully treated, and a careful reading of the work 

 in leisure motnents would doubtless give any one, who 

 had some previous knowledge of the science and some 

 liking for it, a fair grasp of somewhat more than the 

 outlines of this vast and ever-increasing field. Especially 

 interesting, though demanding more than cursory 

 reading, is the concluding chapter on atoms, linkage, 

 and stereo-chemistry. In our earlier days chemists did 

 not so much concern themselves with these things. The 

 determination of mere composition and formuhc furnished 

 enough occupation. But with advance of knowledge 

 it has been found necessary to study what has been 

 called the "atomic architecture of molecules." In the 

 concluding pages this subject is very ably anu lucidly 

 discussed. A new hypothesis is suggested, to which the 

 name of the " screw theory '' is given, which, it is pointed 

 out, may satisfactorily explain those cases of optical 

 activity which are met with in certain bodies, e.g. some 

 terpenes and glycerides, where there is no asymmetrical 

 carbon-atom, and which are consequently not clearly 

 met by van't HotT's ingenious theory. 



The volume is one in the production of which great 

 labour and care must have been expended, and both 

 parts are worthy of commendation. Possibly, however, 

 it would have been advantageous to both, if they had 

 been published separately. J as. Cameron. 



OUR BOOK SHELF. 



Aslronomische Chronologic. By Walter F. Wislicenus. I 

 (Leipzig: B. G. Teubner, 1895.) 



Historians, archaeologists, and astronomers will hail 

 with delight this work, as it fills a gap which for some 

 time past has been very apparent. At the present day, 

 to take one case only, archaologists are busy in Egypt 

 deciphering and unravelling the legion of myths which 

 are there recorded in the many forms and ways peculiar 

 to that country. Many of these myths are, as has been 

 recently more clearly pointed out, purely astronomical 

 in their nature ; and this is perfectly natural when one 

 considers that the Egyptians, or, at any rate, the priests, 

 for these were the chief writers, were astronomers. 

 Archxologists in fathoming these depths are perfectly at 

 home when arch.Lology is in question, but as soon as the 

 astronomical boundary is reached, and astronomy pure 

 has to be attacked, then perfectly dillerent problems are 

 met with. In like manner, the astronomer himself, 

 going from the astronomical to the archaeological side, 

 is also nonplussed, unless he wishes to enter somewhat 

 generally into the study of Egyptology. In the book 

 which we have before us, Dr. Wislicenus gives the 

 historians and archasologists a helping hand, and presents 

 them with the necessary means and ways of solving 

 some of the problems which are generally encountered. 



Without entering too minutely into' the contents of 

 these 150 odd pages, a general survey of the text will 

 best give the reader an idea of their character. 



NO. 1326, VOL. 5 l] 



The two parts, into which the book is divided, deal 

 respectively with the fundamenta of astronomy, and the 

 different methods of computation. 



The former part is concise and brief, and the author 

 in forty-four pages presents the reader with a general 

 summary of the different systems of coordinates used, 

 the different kinds of years, the course of the moon, 

 eclipses, daily and yearly rising and setting of the 

 heavenly bodies. 



The methods of computation in the second part are so 

 arranged that they follow, in the same order,the text in the 

 first. At the commencement of this part Dr. Wislicenus 

 brings together a list of the numerous tables which are 

 used for the solution of chronological problems. These 

 are here given with their full titles, and are explained 

 further on. The remainder of the book is devoted to 

 the solutions themselves, and these are arranged as 

 follows : First, the known and the unknown quantities 

 are separated, then the tables to be used in the problem 

 in question are explained ; following these, typical 

 examples are taken and worked out by the use of the 

 different tables. 



A very full index makes reference easy, and completes 

 what will prove a very useful book. W. J. S. L. 



Die dltesien Karten der Isogoncn, Isoclinen, Isodynxm^n 



By Prof. Dr. G. Hellmann. (Berlin : \. Asher and 



Co., 1895.) 

 This is the fourth of the elegant series of reprints de- 

 voted to classical contributions to meteorology and 

 terrestrial magnetism. It contains seven maps, all 

 excellently reproduced, and representing old standard 

 charts of isogonic, isociinic, and isodynamic lines. The 

 maps portrayed are Halley's Declination Chart of the 

 World, published in 1701 ; Whiston's two maps (l7-l),_ 

 showing lines of equal magnetic Dip in the South of 

 England ; J. C. Wilckes Isociinic Chart of the World 

 in 1768 ; a chart by Humboldt, published in 1804, show- 

 ing Isodynamic lines over part of South .A^merica ; and 

 Hansteen's Isodynamic Charts (1825-26) of North-West 

 Europe and of the world. 



Halley's description of his " New and Correct Sea- 

 Chart of the Whole World, fliewing the Variations of 

 the Compass,' is reprinted, and brief descriptions are 

 given of the other maps. 



Whiston, it may be remembered, suggested that longi- 

 tude might be determined from magnetic inclination, 

 this element being preferred to declination for reasons 

 which he stated as follows : '■ When, therefore, I con- 

 sidered that the Lines of equal Dip could hardly be more 

 irregular than those of the Variation ; I well knew that 

 ;\Iutation was a great deal slower : and that these might 

 probably be useful overall the World ; I conceived great 

 hopes that this way of Application of the Power before 

 us might very probably discover the Longitude." 



Prof. Hellmann contributes a number of biblio- 

 graphical notes, and these, with the maps, make the 

 reprint a compact and useful_work of reference. 



An Elementary Text-book of Hydrostatics. By W. 



Briggs, M.A., and G. H. Bryan, .M.A. Pp. 208. 



(London: W. B. Clive, 1895.) 

 The portions of hydrostatics and pneumatics usually 

 taught to beginners, and required for the matriculation 

 examination of the London University, are concisely and 

 clearly treated in this book. Though evidently con- 

 structed for examinational purposes, the book contains 

 a number of good points. The mathematical formula; 

 are deduced from first principles instead of being stated 

 dogmatically ; so the student is led to rely more upon 

 his real knowledge, and less upon mere memory. This 

 and other commendable features distinguish the volume 

 from ordinary text-books of hydrostatics, while the 

 numerous problems, covering a wide field, furnish clear 

 evidence ot originality. 



