Geology and Natural History. 141 
following down after the more rapidly contracting nucleus. This 
calculation he now makes upon the basis of certain allowable sup- 
positions, where the want of data requires such to be made, and 
tor assumed thicknesses of solid shell of 100, 200, 400, and 800 
miles respectively. 
about 500° for the entire scale, between a temperature somewhat 
exceeding that of the blast-furnace and that of the atmosphere, or 
53° Fahr. And applying the higher of these coefficients to the 
the volume of matter that must be crushed and extruded from the 
2. Metamorphic products from the burning of coai-heds of the 
Lignitie Tertiary in Dakota and Montana.—In this paper, pub- 
, in the Proceedings of the Boston Society of Natural History, 
Jan., 1874 (vol. xvi), Mr. J. A. Allen describes metamorphosed 
