1885.1 ^*5 [Chase. 



should be attached to this higher percentage. The formula for descloizite 

 corresponds to those of adamite, libethenite and olivenite, being : 



Pb2[HO](VAsP)04 + Zn2[H0](VAsP)0i. 



lodyrite. 



Frequently associated with the vanadates of the Sierre Grande, and 

 implanted in calcite in straw yellow to bright suli)hur-yellow imperfect 

 crystals and crystalline masses. The best specimen which could be 

 obtained was sent by the writer to Prof. Gr. vom Rath, who describes 

 them as follows: "The crystals of iodyrite (yellow) are imperfect in 

 "their formation, nevertheless they allow one to determine their form as 

 ''a combination of the hexagonal prism and the basal plane. The des- 

 "cloizite shows large brown crystals of 4™" in size and of older origin, 

 "and smaller ones of light red color and of later origin, attached to the 

 "iodyrite and calcite." 



The spec. grav. of this variety was found to be 5 609, but the analysis 

 was unfortunately lost, it was found qualitatively, however, that it was 

 pure iodide of silver. 



Another variety which is generally associated with the dark variety of 

 descloizite and frequently implanted in it and leaving impressions on its 

 planes, forms minute rounded crystals, rarely 1™™ in size, and shows 

 sometimes little hexagonal prisms with basal plane ; their color is mostly 

 very pale greenish-yellow, seldom brighter. A qualitative test gave also 

 pure iodide of silver. 



University of PennsyUania, April IGth, 1SS5. 



The Chase-Maxwell Ratio. By Pliny Earle Chase, LL.D. 



{Read before the American Philosophical Society, April 17, 1S85.) 



In 1873 (Proc. Amer. Phil. Soc, xii, 394), Chase showed that the ten- 

 dency of particles, in exploded gases, toward primary and secondary 

 centres of oscillation, leads to a permanent vis viva of equilibrium which 

 is f of the vis yi«a of explosive projection, and that the synchronous action 

 of the sun and the earth upon the oscillating particles furnishes a ready 

 method for estimating the sun's mass and distance. He also showed 

 (Ibid, p. 403-5), that the successive planetary positions in the solar 

 system illustrate the influence of aethereal oscillations of a similar char- 

 acter. In 1875 he showed (op. cit., xiv, 651), that the mean velocity 



3 



of expanding gaseous pressure is _ of the corresponding constant velocity 



