August 1, 1902.] 



SCIENCE. 



179 



On the Effect of Electrolytic Condensers in 

 Alternating Current Circuits: A. Trow- 

 bridge and E. R. Wolcott, University 

 of Wisconsin. 



The paper was presented by Professor 

 K. B. Gutlie and described in detail plie- 

 nomena observed in electi-olytic condensers 

 used in alternating-current circuits. It 

 was shown that the custom of regarding 

 such condensers as two ordinary condensers 

 in series was erroneous, as such a view is 

 inadequate to account for the enormous 

 capacities observed. The paper will be 

 published in full elsewhere. 



On the Accuracy of the Zero in a Dynamo- 

 phone: J. BuKKiTT Webb, Stevens In- 

 stitute of Technology. 

 Presented by Professor B. F. Thomas. 

 The dynamophone is a new dynamometer 

 in which the energy transmitted per revo- 

 lution is measured by the twist of the shaft 

 transmitting it, said twist being measured 

 while the shaft is in motion by an electrical 

 method in which no contact is made with 

 the shaft. 



It consists of two armatures or toothed 

 wheels mounted on the shaft at a sufficient 

 distance from each other, each wheel hav- 

 ing a telephone magnet with its coil 

 mounted in front of it in such a way that 

 it can be revolved about the shaft. The 

 distance of the telephone magnets from the 

 armatures is also adjustable. These two 

 telephones are connected in series with a 

 receiving telephone which, when the two 

 telephones are properly adjusted to op- 

 posite phases and equal amplitudes, gives 

 no sound or indicates zero. When the shaft 

 twists under the transmission of a moment 

 the observing telephone must be revolved 

 through the angle of twist to obtain the 

 zero or opposition of phase. 



As in some eases the observing magnet 

 can be revolved through a small angle 

 without perceptibly altering the zero, it is 



advisable to discuss the accuracy of the 

 same, regarded as a question of the inter- 

 ference of waves of the same period with 

 slightly different overtones, and to use a 

 method of observation which avoids the 

 difficulty to a great extent. 



Absorption of Salts in Aqueous Solutions 

 by Powdered Quarts: Lyman J. Briggs, 

 Washington, D. C. 



Finely divided quartz when shaken up 

 with an aqueous solution of a salt possesses 

 the property of increasing the concentra- 

 tion of the solution in the region immedi- 

 ately outside of the solid particle, thus 

 decreasing the concentration of the free 

 solution. Quantitative results showing the 

 relation between concentration and amount 

 of absorption have been obtained for car- 

 bonates, hydroxides and chlorides of sod- 

 ium, potassium and ammonium. 



(a) The absorption of the acid radical 

 was found to be independent of the base. 



(b) The amount of absorption is not a 

 linear function of the concentration, but 

 is relatively greater for dilute solutions. 



071 the Osmotic Pressure of Absorbed 

 Salts: Lyman J. Briggs, Washington, 

 D. C. 



Osmotic pressure of absorbed salts must 

 be the same as in the free portion of the 

 liquid, if equilibrium exists. But the con- 

 centration of the absorbed layer is greater 

 than in the free solution. Therefore, the 

 osmotic pressure of the absorbed layer is 

 not proportional to the concentration of 

 that part of the solution. 



On the Rapid Filtration of Turbid Solu- 

 tions and the Change in Concentration 

 Produced by the Porous Septum: Lyman 

 J. Briggs, Washington, D. C. 

 This paper, which will appear in Bull. 



19, Bureau of Soils, U. S. Department of 



Agriculture, was read by title. 



