Chemistry and Physics. 615 



instruction is intended to facilitate the teacher's individual 

 preferences in regard to the order of presentation. The topics 

 are clearly and simply presented, practically without the 

 employment of mathematical formulas. The book appears to be 

 an excellent one for its intended purpose. h. l.. w. 



5. Organic Compounds of Arsenic and Antimony ; by Gilbert 

 T. Morgan. 8vo, pp. 376. London, 1918 (Longmans, Green and 

 Co.). — We have here an excellent account of these very numerous 

 compounds, some of which, such as cacodyl and its derivatives, 

 have been of great importance in the development of chemical 

 theory, while others, including salvarsan, neosalvarsan, etc., have 

 acquired extensive use in recent times in connection with the 

 treatment of diseases due to pathogenic protozoa. The subject 

 is presented chiefly from the point of view of pure chemistry, but 

 the historical aspects are clearly brought out, the principles as 

 well as many details of the methods of preparation are included, 

 and many references are made to the toxic and medicinal prop- 

 erties of the substances. An extensive bibliography arranged 

 in chronological order is appended. h. l. w. 



6. Edible Oils and Fats; by C. Ainsworth Mitchell. 8vo, 

 pp. 159. London, 1918 (Longmans, Gjeen and Co.). — This is 

 one of a series of Monographs on Industrial Chemistry edited 

 by Sir Edward Thorpe. It gives a concise outline of the chem- 

 ical composition and properties of the more important oils and 

 fats, together with a description of the methods of extracting 

 them from the crude materials and of purifying them. The 

 physical and chemical methods of examining edible oils are also 

 presented, the recent processes for hardening or hydrogenating 

 oils are discussed, the manufacture of artificial butter is 

 described, and an extensive and excellent bibliography of the 

 subject is given. The subject is very well treated from a rather 

 scientific point of view, so that the book is very well adapted 

 for furnishing information in regard to the application of 

 science to this very important field of industry. h. l. w. 



7. Scattering of Light by Bust-free Air, with Artificial Repro- 

 duction of the Blue Sky. — A very clear account of some recent 

 qualitative experiments on the scattering of light by gas mole- 

 cules has just been published by their author, the Hon. R. J. 

 Strutt. The vessel which contained the gas consisted of two 

 brass tubes, each of diameter 1-5 inches, the axes of which inter- 

 sected at right angles. To avoid circumlocutions we shall refer 

 to the^parts of this compound tube as if its axes formed a dia- 

 gram of ordinary rectangular coordinate axes. The light from 

 the source (usually a hand-regulated carbon arc of 12 amperes) 

 passed toward the origin of coordinates (or intersection of the 

 brass tubes) along the negative portion of the axis of x. It was 

 first condensed by a quartz lens, then the heat rays were 

 absorbed by the water in a cell having plane parallel quartz win- 



Am. Jour. Sci. — Fourth Sertes, Vol. XLVI, No. 274. — October, 1918. 



27 



