T. 8. Hunt—The Decay of Rocks. 191 
decomposition. 
A memoir, by Fournet, published in 1834,* gives many 
facts regarding the early observations on rock-decay. Its 
rvations of Pallas, w 
Siberia (1768-1774), noticed hills “that seemed composed of 
7 
* 
these was due to original concentric structure, was rejected by 
Fournet. : 
masses rest upon each other, decayed matter filling the inter- 
stices.* In 1825, T. W. Webster noticed the same example, 
the decayed greenstone.’ . Again, in 1858, W. P. Blake ce 
described the production at rounded masses both of sandstone 
lar locks, separated by joints admitting water to all si es, 
“att 
OVEr, the , 
California, lying on an uneven surface of the same rock, : 
ue to the manner in which the rock decomposes, and not to © 
* Ann. de Ch. et de Phys. [2] v, 225-256, 
* Mem. Amer. Acad. Sciences, Ist Series, iv, 201.- 
5 Boston Journ. Philos, and Arts, ii, 285. 
