458 Scientific Indulgence. 



liquid into the capillary. During the determination of the elec- 

 trical resistance of the thread of mercury in the capillary, the 

 system of tubes is kept within - 01° C. of a given temperature by 

 means of a water-bath, toluene regulator, etc. 



The length of the capillary bore is easily measured by means 

 of a comparator. From the numbers expressing the length of 

 the capillary, the resistance of the thread of mercury, and the 

 specific electrical conductivity of mercury, the square of the 

 mean radius of the capillary bore can be calculated at once. A 

 small correction was added to the length of the bore to allow for 

 the curvature of the stream lines at each end of the capillary 

 tube. The squares of the mean radii of three tubes were found 

 to be respectively 0-002304 mma , O-004406 mma , and 0-004192 mraa , with 

 an error of about 0-0()0002 m,na . Thus the result obtained for a 

 tube of , 064.74 mm radius is about 20 times as good as for the 

 hypothetical case first cited for a radius of O^OS""". — Phil. Mag. 

 (6), xxi, 336. h. s. u. 



7. An Introduction to Thermodynamics for Engineering 

 Students ; by John Mills. Pp. viii, 136 ; 61 figures. New York, 

 1910 (Ginn & Co.). — This is a text written for the use of classes 

 in engineering, and intended as a preparation for more advanced 

 work in the application of thermodynamics to heat engines. It 

 is divided into five chapters. The first contains a concise sum- 

 mary of the general principles of thermodynamics, and the 

 remaining four the applications to gases, water and saturated 

 vapor, superheated steam, and the flow of steam and gases respec- 

 tively. At the end of each of these last four chapters is appended 

 a summary of the formulas which have been developed and a 

 considerable number of graded problems with their solutions. 

 This last feature frees the main body of the text from the very 

 necessary but cumbersome explanations of details, and allows the 

 development of the theories involved to be shown in a truer per- 

 spective than if such details were interpolated in the exposition. 

 Graphical methods (the temperature-entropy, Boulvin, and other 

 diagrams) are emphasized, but not to the exclusion of the analyti- 

 cal methods. The ground covered is about that customary in 

 first courses in this subject as given in most technical schools in 

 this country. The subject matter is possibly too restricted in 

 scope for a wide field of usefulness, and the discussion of the 

 second law of thermodynamics is marred by a mistaken interpre- 

 tation of Clausius's statement of it. But on the whole, the end 

 which the author had in mind in writing the book has been suc- 

 cessfully attained. l. p. w. 



II. Geology and Mineralogy - . 



1. Denudation and Erosion in the Southern Appalachian 

 Region ; by L. C. Glenn. Prof. Paper 72, IT; S. Geol. Surv., 

 1911. Pp. 137, 5 plates, 1 figure. — A detailed study of the 

 effects of deforestation, overgrazing, and "agricultural butchery" 



