558 proceedings: philosophical society 



water could be detected after allowing the water to stand over night. 

 All subsequent experiments showed that this is not the case, but rather 

 that an electrolytic process was taking place by which the silver was 

 passing into solution at the rate of about 0.006 mg. per hour from a 

 4 gram deposit of silver on platinum. Confirming this it was shown 

 by a galvanometer that a current actually passed from the silver through 

 the water to the platinum. In washing the deposits over night this 

 effect becomes appreciable. The paper was discussed by Messrs. 

 BuEGEss and C. A. Briggs. 



Mr. M. James then spoke on .4 conducting paint. An electrically 

 conducting paint has been obtained through the action of hydro- 

 chloric acid on bronze powder. The resistance of a paint film depends 

 largely upon the surface to be painted. The resistance increases with 

 time; the rate of change, however, decreasing. For such surfaces as 

 glass, wood, and paper, the resistance increases about 30 per cent in 

 two months, and then is fairly constant. The resistivity of a painted 

 surface is about 1000 times that of copper. The paper was discussed 

 by Messrs. Swann. Priestly, and Bessaches. 



The 757th meeting Avas held on May 8, 1915, at the Bureau of Stand- 

 ards, President Eichelberger in the chair; about 90 persons present. 

 President Eichelberger called upon Vice-President Humphreys to take 

 the chair for the meeting. Mr. Humphreys introduced the speaker 

 of the evening. Prof. E. Northrup, of Princeton University, who gave 

 an experimental lecture on Some physical properties of matter at high 

 temperatures. Temperature was defined as a condition of matter which 

 results from the disorganized motion of its molecules or atoms, as con- 

 trasted with any organized motion which is impressed upon a mass 

 as a whole. It was pointed out that any body tends to acquire a dis- 

 organized motion of its ultimate parts, called its temperature, because 

 this kind of motion is the most probable of all motions. A ''visil>le 

 molecules apparatus" was exhibited which illustrated the above con- 

 ception of temperature as well as some of the fundamental principles 

 belonging to the kinetic theory of gases. With this apparatus, in which 

 16,000 one-sixteenth-inch steel balls were caused to move in the manner 

 of gas molecules, experiments were shown to illustrate change of pres- 

 sure with temperature, the voliunc being constant, and change of 

 volume with temperature the pressure being constant. With the aid 

 of accessories attached to this apparatus the viscosity of a gas was illus- 

 trated and an imitation was given of the Brownianniovements. Other 

 experiments which could be performed, with this apparatus were de- 

 scribed. It was stated that temperature was a unique condition of mat- 

 ter and that it affects its manifested properties more than any other 

 single condition to which matter may l)e subjected. 



The problem of the electrical conduction of matter throughout 

 the producible temperature range of some 4000°C. was discussed. 

 Methods and apparatus were described and shown for experimentally 

 studying the electrical conduction of matter in its solid, liciuid, and 



