October 21, 1898.] 



SCIENCE. 



531 



The Hysteresis of Iron and Steel at Ordinary 

 Temperatures and at the Temperature of Solid 

 Carbon Dioxide. By A. M. Thiessen, 

 Ithaca, N. Y. 



It was found that the hysteresis loss for 

 constant magnetizing fields increases with 

 the temperature if the field is weak, but 

 the opposite is the case when the iron is 

 nearly saturated. ' 



Some Determinations of Dielectric Strength. 



By Professor Thomas Gray, Terre 



Haute, Ind. 



Step-up ring transformers were used 

 and the potential diiference was determined 

 by an electrometer. It was found that the 

 dielectric strength for air is the same for al- 

 ternating currents of ordinary frequency as 

 it is for static charges. 



A Study of Standard Meter Scales ruled on 



Nickel, Silver and Glass. By Professor T>. 



C. Miller, Cleveland, Ohio. 



After an exhaustive study of scales of 



various kinds Professor Miller concludes that 



nickel scales are far superior to those in 



common use, and indeed as good as platinum 



iridium, except that they have a somewhat 



higher coefiicient of expansion. His nickel 



bar, ma4e by the Geneva Society, is very 



accurately divided, and he has calibrated 



it throughout by the international method. 



An Instrument for Measuring Radiance. By 



Professor Knut Angstrom. 



The instrument was exhibited by Mr. E. 

 S. Ferry, and consists essentially of two 

 bolometer strips, one of which is heated by 

 the radiance to be measured and the other 

 is heated to the same temperature by an 

 electric current, from which the absolute 

 valve of the radiance may be calculated. 



A Redetermination of the Ampere. By Geo. 



W. Patterson and Karl E. Guthe, Ann 



Arbor, Mich. 



The authors used an electrodynamom- 

 eter the moment of whose coil was bal- 



anced by the torsion of a wire of small elas- 

 tic fatigue. The work seems to have been 

 done with extraordinary care and gives 

 0.0011192 grams per sec. per ampere for 

 the electrochemical equivalent of silver. 

 This reconciles the difference between 

 Rowland's value for the mechanical equiva- 

 lent of heat and that obtained by electrical 

 methods. The paper occasioned a great 

 deal of favorable comment. 

 Progress in the Exploration of the Air with 

 Kites at the Blue Hill Observatory. By A. 

 Lawrence Rotch, Director. 

 On the Osmotic Pressure of certain Ether Solu- 

 tions and the Validity of the Boyle- VanH 

 Hoff Law. By Professor H. M. Good- 

 win and Geo. K. Burgess, Boston, 

 Mass. 



It was shown that the Boyle- Van't Hoflf 

 law holds as a first approximation only. 

 On the Dielectric Constant and Electrical Con- 

 ductivity of Liquid Ammonia. By Profes- 

 sor H. M. Goodwin and Maurice De 

 Kay Thompson, Boston, Mass. 

 It is found that the dielectric constant of 

 liquid ammonia is less than it is for water, 

 while the electrical conductivity of solu- 

 tions of salts in ammonia is greater than it 

 is for solutions of the same salts in water. 

 The two reports and five papers follow- 

 ing were read iu joint session with Section A. 

 Report on the Recent Progress in the Dynamics 

 of Solids and Fluids. By Professor Ernest 

 W. Brown, of Haverford College, Pa. 

 [To be printed in Science.] 

 Report on the Recent Progress in the Mathe- 

 matical Theory of Electricity and Magnetism. 

 By Professor Arthur G. Webster. 

 Tlie Mass and Moment of Inertia of the Earth^s 

 Atmosphere. By Professor E. S. Wood- 

 ward, Columbia University, New York. 

 Professor Woodward pointed out our 

 ignorance of the necessary data and gave the 

 results arrived at by making various hy- 

 potheses. 



