166 Prof. D, Kirkwood on the Nebular Hypothesis. 
out the entire mass. That the interior of our planet is in a.state 
of igneous fluidity, or has, at least, an extremely high tempera- 
ture, is now very generally admitted. As we descend from the 
surface we find a regular increase of heat, varying indeed for 
different localities, partly no doubt, on account of the different 
pi greet upheaving power by which not only mountains, but 
islan 
y radiation from the surface. “There is no small reason,” says 
Professor Hitchcock, “to suppose that the globe underwent nu- 
merous changes previous to the time when animals were placed 
pon it ; that, in fact, the time was when the whole matter of 
nt on the first transition of matter condensing from the gaseo-fluid into the solid 
: en, bd. xxxix, S. 93—100. 
Pr; Idt’s Cosmos, vol. i. p. ; : 
See Proceedings of the American Association for the Advancement of Science, 
p. 102, 
similarity of lava, wherever found, and the close agreement as to compo- 
ing through and intersecting the walls of modern volcanoes, are proofs that all such 
roves op a common origin, and are due, as w: 
~ phenomena of earthquakes, to fi i fl ani : earth. 
Portlock’s Ruddnentiry Cookapy:: ang eta on the yh hated paee ee 
F Sod — ches of Hopkins and Hennessy have led to different results in regard to 
- k ickness of the earth's crust. See Trans. of the Rey. Soc. for 1839, p- 381; 
for {i0, p. 198; for 1342, p. 43; for 1851, Part Il, p. 495. Also, this Journal 
Ex “ee 1, 1852, p. 271, and for May, 1853, p. 126, For “some suggestions 
Plocau tion of the primitive Incandescent condition of the Earth and the other 
» See Monthly Notices of the Roy, Astro. Soc. for January 13th, 1854- 
