88 proceedings: philosophical society 



THE PHILOSOPHICAL SOCIETY OF WASHINGTON 



The 729th meetmg was held on November 8, 1913, at the Cosmos 

 Club, Vice President Eichelberger in the chair; 38 persons present. The 

 minutes of the 728th meeting were read and approved. 



Mr. R. B. SosMAN presented a paper, illustrated by lantern slides, 

 giving the results of an investigation by himself and Mr. A. L. Day on 

 A method for determining the expansion of liquid metals. After reviewing 

 existing and rather conflicting data on the change in volume on fusion of 

 various rocks, the apparatus designed for such volume determinations 

 of metals and of solid and liquid silicates from 250° to 1600° was de- 

 scribed. The fundamental constant is the expansion coefficient of arti- 

 ficial graphite given by formula 10*^13 = 0.55 + 0.0016^ Volume measure- 

 ments on quartz up to 1600° show a dilatation which increases rapidly 

 as the inversion point of 575° is approached. Above this temperature 

 quartz contracts slightly. At about 1300° there begins a second and 

 (under these conditions) irreversible dilatation. Granite has a curve of 

 similar form. The volume of diabase glass was determined up to 1250° 

 and compared with Barus' well-known values. A simple explanation 

 of some of the conflicting features of his observations has been found. 



The paper was discussed by Mr. Burgess. 



Mr. A. W. Gray then spoke on Some peculiarities of invar. He de- 

 scribed some of the results obtained by himself and previous observers 

 in measuring the thermal expansion of invar. Numerous lantern slides 

 were exhibited to show various peculiarities of the alloy, method and 

 apparatus used by the speaker in determining expansivities, the precision 

 obtained in measuring elongations by the use of both freely suspended 

 and upwardly stretched wires, and the uniformity of temperature easily 

 secured in an electric furnace of the type used for most of the work. One 

 most striking feature is that at temperatures above- about 170° invar may 

 follow with considerable regularity either of two different expansion 

 curves, without ever jumping from one to the other except, perhaps, 

 when close to this critical temperature. Further above about 220° for 

 the upper curve and about 280° for the lower one, the expansivity of in- 

 var appears to be identical with that previously found for a specimen of 

 Bessemer steel. Under some conditions the same piece of invar may, 

 at high temperatures, expand noticeably faster than Bessemer steel. 

 Comment was made upon progressive shortening produced by repeated 

 alternations of temperature between 20° and 150°. 



J. A. Fleming, Secretary. 



