398 



SCIENCE. 



[N. S. Vol. XXIV. No. 613. 



The book is designed to be readable even by 

 those without extensive mathematical or scien- 

 tific training: to give a general view of the 

 results that astronomers have obtained in the 

 course of their investigations; and to reveal 

 something of that spirit which inspires scien- 

 tific work. Astronomers to-day, perhaps more 

 than ever before are endeavoring to solve 

 great problems. The investigations leading 

 to these ends are diverse, extended and many- 

 sided, and the data drawn from the various 

 sources often admit of widely different inter- 

 pretations. In some departments advance 

 comes from adhering to the hard and fast 

 facts derived from exact measurements, in 

 others from speculative inquiries based upon 

 data that are more or less insecure, founded 

 upon such observations as have been made to 

 the present time. Often contradictory work- 

 ing hypotheses lie so near the limits of inde- 

 termination that one is as plausible as the 

 other, and this is so in many of the problems 

 of gTeat human interest as they stand to-day. 

 Hence it is riot always easy to decide between 

 rival hypotheses, for the overbalancing data 

 favorable to one to-day may by fresh acces- 

 sions to knowledge be turned to-morrow in 

 favor of the other. In producing a work on 

 astronomy for the general reader, and for the 

 student as well, some attempt should be made 

 to give that broadening view that the subject 

 affords, not only by reason of its established 

 facts but from the outlook afforded by investi- 

 gations now in progress. The latter requires 

 the inclusion of outlines of various theories 

 still in formation, to be accepted or rejected 

 according to the evidence that may be ad- 

 duced in favor of or against them. In his 

 ' Introduction to Astronomy,' Professor Moul- 

 ton has many references to unsettled questions. 

 He has always considered them with caution, 

 giving briefly the arguments on both sides of 

 debatable points, without commending to the 

 reader one view rather than the other. The 

 chapter on the evolution of the solar system, 

 which may be regarded as the distinctive one 

 of the book, deserves special mention, since it 

 deals largely with the arguments tending to 

 prove the general insufficiency of the Laplacian 



ring nebular hypothesis, which has so long 

 held a place in elementary texts, and to the 

 exposition of the new spiral nebular theory 

 developed by Professors Chamberlain and 

 Moulton. Even in reference to the latter the 

 author cautions the reader against the too 

 hasty acceptance of it as final, for much still 

 remains to be accomplished in the way of 

 quantitative determinations before this theory 

 can take its place among the accepted results 

 of science. 



W. J. HUSSEY. 



Ann Arbor, Michigan. 



Introduction to General Inorganic Chemistry. 



By Alexander Smith. 8vo, pp. xviii -t- 



780. New York, The Century Co. 1906. 



This unusually excellent text-book is in- 

 tended primarily for beginners in college 

 courses. The author has wisely made the 

 elucidation of chemical theory the main fea- 

 ture of the book, but the descriptive part has 

 been well chosen for the purpose in view. 

 Laboratory experiments are used as the basis 

 of treatment, and the theories are thus ex- 

 plained in a very clear and satisfactory way. 

 The subject is treated from the most modern 

 standpoint, but this has been done without 

 giving undue prominence to the newer the- 

 ories. 



An important feature of the book is found 

 in the numerous references to previous pages, 

 which enable the reader to refresh his memory 

 in regard to matters already discussed. Other 

 points attracting attention are a diagram 

 showing the solubility curves of eighteen im- 

 portant salts, a table showing the actual and 

 molar solubilities at 18° of more than a hun- 

 dred salts, the use of the single or double 

 arrow in place of the usual sign of equality 

 in chemical equations, the introduction of 

 many suggestive exercises or questions for 

 students, and a serviceable index. 



The course here presented is undoubtedly a 

 long and difficult one for the average student, 

 who relies mostly upon memory and possesses 

 little or no power of reasoning; for it com- 

 prises practically the whole body of modern 

 chemical theory, which is not grasped easily 

 by the chemically vacant mind. However, 



