78 Scientific Intelligence. 



general the book is an excellent example of what a text-book on 

 a physical subject for the use of serious students should be. 



H. A. B. 



13. Aj^plied Mechanics for Engineers ; by E. L. Hanoock. 

 Pp. xi, 385. New York, 1909 (TheMacmillan Co.).— The author's 

 main purpose, as stated in his preface, is to emphasize the appli- 

 cations of mechanical theory to practical engineering problems. 

 This design appears to have been successfully carried out ; the 

 numerous problems given are good examples of mechanical prin- 

 ciples and are at the same time stated in terms of angle-irons, 

 fly wheels, governors, and other concrete mechanisms. On the 

 other hand the physicist or mathematician will find much to com- 

 plain of in the loose and often inaccurate definitions and state- 

 ments of fundamental laws and principles. It would seem that 

 even for student's of engineering a little more attention to logical 

 relations might be of value. h. a. b. 



14. The Absorption Spectra of Solutions ; by Harry C. Jones 

 and John A. Anderson. Pp. 110 with 81 plates. Publication No. 

 110, Carnegie Institution of Washington, 1909. — This investiga- 

 tion is a continuation of the work of Jones and Uhler which was 

 begun in 1905 (see Carnegie Publication No. 60). The amount 

 of work performed by the authors is so great as to preclude the 

 possibility of doing it justice in this brief review. Nevertheless 

 the following salient points are especially worthy of notice. 



The absorption spectra of solutions, in various solvents, of 

 twenty-four colored salts were photographed from A 2000 to A, 

 7400 and studied in detail. Some idea of the scope and thorough- 

 ness of the investigation may be formed from the fact that 

 about 1200 solutions were studied and that 1138 photographic 

 strips, each corresponding to a different solution, are reproduced 

 in eighty excellent, full-page plates. In general, the authors 

 have been able to draw definite conclusions as to whether a given 

 absorption band is due to ions, or to atoms, or to undissociated 

 molecules, and also as to the existence and relative importance of 

 solvates. Undoubtedly the most interesting and valuable results 

 were obtained in connection with the spectra of the three rare 

 earths investigated and especially in the case of neodymium 

 chloride. When this salt was dissolved in mixtures of varying 

 proportions of water and methyl alcohol it was found that the 

 apparent shifts in the bands were not real, as has usually- been 

 believed heretofore, but that the effect observed is the result of 

 the superposition of two distinct sets of absorption bands, the 

 one set being identical with that exhibited by solutions in 

 pure water and the other by solutions in anhydrous methyl 

 alcohol. Ethyl alcohol and water gave similar results. 



In conclusion, attention should be called to the source of ultra- 

 violet light used by Jones and Anderson, which is a marked 

 improvement over anything employed in the past. Taken as a 

 whole, Publication No. 110 is a valuable contribution to the sub- 

 ject of solutions and absorption spectra. h. s. it. 





