Chemistry and Physics. 331 



centrifugal force, are automatically driven out by the same means. 

 It is stated that it is possible in this way to obtain air so much 

 enriched in oxygen as to make it much more effective in the 

 combustion of fuel, and it is expected that the applications of 

 the process will be important in metallurgical operations, in the 

 production of steam, etc. It is expected, also, that the method 

 will be used in the treatment of illuminating gas in order to 

 separate a mixture rich in hydrogen from one of higher heating 

 and illuminating power, and also for separating a large part of 

 the carbon dioxide from blast-furnace gases, in order to make 

 them more efficient. — Chem. JS^eics, Ixxxviii, 68, 76. h. l. w. 



5. A Double Salt of Potassium and Barium N'itrates. — A 

 double salt having the formula K^Ba (XOJ^ has been prepared 

 by Wm. K. Wallbridge of the Sheffield Laboratory. The com- 

 pound is remarkable because double salts of alkali metals and 

 barium have been entirely unknown, and also because double 

 nitrates are very rare. For these two reasons the salt is a very 

 unusual one, and one whose existence would not be expected from 

 analogy. The salt crystallizes from solutions containing the com- 

 ponents under considerably varying conditions, but the crystals 

 are very rough and opaque. They are tetrahedral in habit, like 

 simple barium nitrate, and the author suggests that it is possible 

 that their structure is pseudomorphic. — Amer. Chem. Joiir.^ xxx, 

 154. H. L. w. 



6. Light Waves and their Uses; by A. A. Michelsox. 166 

 pp. Decennial Publications of the University of Chicago, 1903. 

 — The eight lectures which make up the present volume were 

 delivered at the Lowell Institute in 1899, and it is a source of 

 satisfaction to all who are interested in physics that their publi- 

 cation has not been longer delayed. Among instruments of pre- 

 cision there are few which rival Professor Michelson's interfero- 

 meter in simplicity, in accuracy and in wide range of application, 

 and perhaps none. which is so interesting in respect to the natural 

 phenomena which it incidentally illustrates. The author has suc- 

 ceeded in giving an admirably clear and simple account of the 

 phenomena of interference, and of the many important researches 

 which he has carried out by means of the interferometer and the 

 echelon spectroscope. The presentation is so skilfully managed 

 that the book can scarcely fail to hold the interest of the general 

 reader, while at the same time physicists and astronomers will 

 find in it much valuable information. h. a. b. 



7. The Sub- Mechanics of the TIni-cerse ; by O. Reynolds. 

 xvii + 254 pp. Published for the Royal Society of London. 

 Cambridge, 1903. — In this memoir Professor Reynolds believes 

 that he has shown that there is " one, and only one, conceivable 

 purely mechanical system capable of accounting for all the phys- 

 ical evidence, as we know it, in the L^niverse." Whether this 

 belief is correct in whole or in part, whether the author's funda- 

 mental hypotheses are reconcilable with all known facts, and, 

 more particularly, whether, if this be a legitimate explanation, it 



