184 



SCIENCE. 



[N. S. Vol. XVII. No. 422. 



lines of force has been definitely estab- 

 lished from theoretical considerations. 

 Voigt has obtained equations which indi- 

 cate not only this result, but also double 

 refraction at right angles to the lines of 

 force. The experimental results of Voigt 

 apparently confirm this conclusion for 

 glass and sodium vapor. The author calls 

 attention to the fact that the results ob- 

 tained by Voigt might be due to the Fara- 

 day effect. He finds this to be the case 

 with glass, but confirms Voigt 's conclusion 

 for sodium vapor. 



The next paper was by Professor A. 

 Wilmer Duff, on the 'Viscosity of Liquids 

 at Low Rates of Shear.' According to 

 ideas developed by Poisson, Maxwell, and 

 others, a liquid differs from a solid in 

 having either a low modulus of rigidity or 

 a high rate of relaxation under shearing 

 stress, and the coefficient of viscosity con- 

 tains a term that varies inversely as the 

 rate of shear. Experiments by Professor 

 Duff, made at a rate of shear about 1,000 

 times lower than the lowest in Poisenille's 

 experiments, seem to show that, while the 

 coefficient of viscosity of kerosene is the 

 same within rates of shear that vary as 

 50,000 to 1, that of water, is slightly larger 

 at the low rates of shear than at the high 

 rates used in Poisenille's experiments. 

 This might be interpreted as indicating a 

 definite, although very narrow, limit of 

 perfect elasticity for water under shearing 

 stresses. 



'Results of Determinations of the Me- 

 chanical Efficiency of Musical Instru- 

 ments,' were presented by Professor A. G. 

 Webster. The determinations were made 

 with the help of the apparatus designed by 

 the author for sound measurements, which 

 was described at the April, 1902, meeting 

 of the- Society. The efficiencies obtained 

 were extremely small, indicating that 

 soi;nd-pr.oducing machines are even more 



inefficient than those used in producing 

 light. 



A paper by Dr. Hersehel C. Parker on 

 'Experiments with Very Brief Electrical 

 Contacts' gave an account of tests of a 

 gravity contact key devised by Dr. Charles 

 Forbes. The apparatus itself had been 

 exhibited at a former meeting. Dr. Parker 

 finds that reliable contacts can be obtained 

 ranging in duration from 0.1 sec. to about 

 0.00001 sec. 



Brief papers by Professor W. J. Hum- 

 phreys, on 'A Comprehensive Boyle's Law 

 Apparatus' and 'A Lecture-room Method 

 of Analyzing Irregular Electric Currents,' 

 dealt with these subjects from the peda- 

 gogical standpoint. 



The last paper on the program was by 

 Dr. C. A. Skinner, on the 'Critical Cur- 

 rent Density and Cathode Drop in Vacuum 

 Tubes.' The author referred to the differ- 

 ence in the formulae obtained by Stark and 

 himself giving a relation between cathode 

 drop, current density, and pressure. Dr. 

 Skinner explains the difference as due to 

 the fact that wire electrodes were used in 

 the experiments of Stark, while in the ease 

 of his own experiments disk electrodes had 

 been used. 



As one day proved too short a time to 

 complete the program of the society, the 

 joint meeting with Section B was contin- 

 ued on Thursday, January 1, a number of 

 the above-mentioned papers being pre- 

 sented on that day. The meeting may 

 properly be regarded as one of the most in- 

 teresting and successful which the society 

 has ever held. Ernest Meeeitt, 



Secretary. 



SCIENTIFIC BOOKS. 

 A Nature Wooing at Ormond hy the Sea. By 

 W. S. Blatchley, author of 'Gleanings 

 from Nature.' Indianapolis, The Nature 

 Publishing Company. 1902. 12mo. Pp. 

 245. 

 The author went to Florida in the early 



