APEn. 9, 1897.] 



SCIENCE. 



589 



more recent date ; still, it has become the sub- 

 ject of very general attention. Separate or 

 special chairs devoted to this branch have 

 been created at several of the foreign technical 

 schools, and journals intended for the publica- 

 tion of its distinctive methods and practices 

 have been established. EflForts are now being 

 made to gather in the widely spread literature 

 relating to this subject. The volume before us 

 presents a very full, although not exhaustive, 

 treatment of all the sources of electric energy, 

 the dynamo excepted. The author aims, in 

 this volume, to give a concise account of the 

 various forms of primary batteries and storage 

 cells which have been devised at various times, 

 and adds information in regard to the same 

 which will prove helpful both to those who are 

 engaged in promoting electro-chemical pro- 

 cesses and to students who are seeking to gain 

 for themselves as complete a knowledge of this 

 subject as is possible. Some idea of the con- 

 tents of the volume may be obtained from the 

 following topics : A. Galvanic Batteries : 1. 

 Batteries with one electrolyte. 2. Batteries 

 with two electrolytes. 3. Dry batteries. 4. 

 Normal batteries. 5. Suggestions for the con- 

 struction of batteries and their components. 

 B. Batteries serving for production of electric 

 energy directly from carbon. C. Gas batteries. 

 D. Thermopiles. E. Accumulators. 



The author has treated his subject under- 

 standingly and has prepared a work which will 

 prove of great value to all interested in applied 

 electricity. It is his purpose, at an early date, 

 to issue companion volumes, dealing with the 

 application of electricity to metallurgy, to gal- 

 vanoplastic processes, to chemical analysis and 

 to industrial chemistry. The subject-matter in 

 these later volumes is to be discussed in a 

 thoroughly practical manner. 



Edgar F. Smith. 



TJniveesity of Pennsylvania. 



SCIENTIFIC JOURNALS. 

 AMERICAN JOURNAL OF SCIENCE. 



The April number opens with an extended 

 article by A. M. Mayer, giving the results of a 

 long series of investigations of the phenomena 

 of flotation of disks and rings of metal. The 

 author briefly reviews the early literature on 



the subject and notes the erroneous statement 

 often repeated in treatises on physics that a film 

 of grease is necessary to float a piece of metal 

 on a water surface. With respect to this point 

 his results confirm the idea that the film of 

 air which adheres to the body is essential to its 

 floating, since rings of metals, as also rods of 

 glass, sank in water if they had been heated and 

 the air expelled, but regained their power of 

 flotation after being exposed to the air for some 

 10 or 15 minutes. The disks experimented upon 

 were made of aluminum, but the rings were 

 made also of other metals, as iron, copper, 

 brass, etc. The method of experimenting 

 made possible the accurate determination of 

 the depression of the water surface and also of 

 the weight required to just break it and allow 

 the disks or rings to sink. In the case of the 

 rings the form of the water surface was more 

 complex and called for special investigation. 

 The equation of forces acting upon the disk of 

 aluminum allowed finally of a determination of 

 the surface tension of water, which was found 

 to be .0791 as the mean of three determinations. 

 With rings of diiferent metals the value ob- 

 tained was .0809. The mean of twenty-eight 

 determinations of this constant by various 

 physicists during the past sixty years is .0772. 

 The surface tension of a solution of sodium 

 chloride of a density of 1.2 was also determined 

 and found to be .0860 (using the value .0772 

 for water). 



George F. Becker contributes a paper on the 

 method of computing diffusion with special 

 reference to the difiusion in the viscous fluids 

 as applied to geological phenomena. This is in 

 connection with an earlier discussion by the 

 same author on rock differentiation, published 

 in the January number. E. O. Hovey discusses 

 the rock of a dike in the Connecticut Triassic 

 area, a few miles east of New Haven. This 

 rock is remarkable in that it departs from the 

 usual diabase character which so remarkably 

 characterizes the Triassic igneous rocks of 

 the entire Atlantic border. It is distinctly acid 

 in character and seems to belong to the group 

 of keratophyres. F. A. Gooch and C. F. 

 Walker discuss the application of iodic acid to 

 the analysis of iodides. The granitic rocks of 

 the Pyramid Peak district in the Sierra Nevadas 



