268 ELWOOD S. MOORE 
seen which are partially dissolved and the material redeposited 
in a granular condition. 
It is more difficult to account for the agent which dissolved the 
silica in this area. Hot water would be an active agent if present, 
and although the heat developed during the mountain-building 
period must have been considerable there are no metamorphic 
Fic. 6.—Photomicrograph illustrating solution and transfer of silica. 45 
changes of sufficient importance to justify the conclusion that the 
heat became great enough to effect the solvent action of the meteoric 
water to any appreciable extent. The presence of carbonic acid 
doubtless played a part but the extent of this action is uncertain. 
Alkali waters may have produced important effects but we have 
no proof that they were present in large amounts and we must 
therefore turn to organic acids as a recognized agent of importance 
