580 RECORD OF MEETINGS OF THE 



therefore probable that the argon was associated with the air 

 held in the powdered mineral which was completely driven off 

 only upon heating it. 



"It therefore appears that if helium is contained in carnotite 

 at all, it exists in far smaller amount than would be expected 

 from the quantity of radium present. Put it is probable that 

 this absence of helium may be explained by the physical proper- 

 ties of the mineral. Carnotite is a very fine powder which is 

 usually found disseminated through sandstone. Now even 

 the most compact specimens of this, sandstone containing 

 carnotite are quite permeable to gases. This was shown by 

 closing one end of a glass tube with a piece of the mineral about 

 2 cm. in thickness, and filling it with illuminating gas over 

 water. In a few minutes the water rose a distance of 6-7 cm. 

 in the tube. If we then assume helium to be formed in this 

 mineral by the disintegration of the radium it appears reason- 

 able to suppose that it rapidly diffuses away. The minerals 

 that contain helium are known to be massive, impervious 

 substances, which are therefore able to retain the helium formed 

 in them. 



"This explanation of the absence of helium from carnotite 

 appears to be supported by the views of Travers 1 on the state 

 in which helium exists in minerals. According to him the 

 helium is present in the minerals in a state of super-saturated 

 solid solution; the minerals being impermeable to the gas at 

 ordinary temperatures, the velocity with which equilibrium 

 is established between the helium in solution and the helium 

 in the gaseous phase is very small, but increases rapidly with 

 rise of temperature. In the case of carnotite, however, the 

 mineral is permeable to the gas at ordinary temperatures, and 

 therefore we could not expect to find any appreciable amount 

 of helium in this mineral." 



Mr. James stated that the stripping of the grit from the 

 crest of the second anticline of the Shawangunk Mountain 

 (Darton, Rep. 47, N.Y. State Mus.) appears to be due to a 

 slight cross fold by anticlinal fracture and erosion, as the rocks 

 at the southwest end of the eroded area show an upward pitch. 

 » Nature, Jan. 12, 1905. 



