AMERICAN GEOLOGY DECADE OF 1870-1879. 553 



He described sink holes and what are evidently stylolites, the true 

 character of which he did not recognize, but regarded as doubtless 

 due to the same physical disturbances. The elevation referred to and 

 the belts of mineral land in the district were formed, he conceived, 

 from groups of fissures or faults in the Plutonic and Azoic rocks 

 beneath, which were themselves produced by mechanical forces evi- 

 dently generated by internal heat. Water entering between the beds 

 would percolate downward through these lines of fracture, where it 

 would come in contact with intensely heated matter under a pressure 

 of several hundred feet of overlying rock. If the temperature was 

 sufficient the water would be converted into steam or elastic vapor, 

 which might possess sufficient mechanical power to bring about the 

 elevation. During the early formation of the stratified rocks, partic- 

 ularly the Potsdam sandstone, the resistance to this expansive force 

 would be comparatively little, since vent for the steam would be easily 

 found through the loosely accumulated sand; but as layer after layer 

 was added to the strata and the more compact limestone began to form 

 and harden above it, resistance would increase until to overcome it a 

 general lifting of the strata would take place, by which escape would 

 be effected through fissures in the rock along the line of those original 

 faults in the Plutonic rocks below. 



A microscopic examination of the sand grains from the disintegrated 

 Potsdam sandstone having revealed the crystalline nature of the gran- 

 ules, due, as we now know, to the deposition of interstitial silica, he con- 

 ceived, as did Whitney (p. -i6!»), that the entire deposit was of chemical 

 origin. 



Supposing Iceland should be submerged to a considerable depth beneath the 

 ocean, and those plains situated about 30 miles from that noted volcano Hecla, 

 known now to be full of heated springs, steaming fissures, and boiling geysers, 

 whose waters hold a large amount of silica in solution that is now being deposited 

 on the surface around those places, were pouring their waters into the ocean above, 

 should we not have there on a small scale what perhaps existed on a very large scale 

 during our sandstone formation? 



Perhaps so. Who shall say \ 



Like many men of slight training, Murrish failed to give proper 

 weight to the evidence gathered and was led into many errors, the 

 most serious of which was that of assuming that the Lower Maghesian 

 limestone might prove to be an ore-bearing stratum — this in spite of 

 the opinion to the contrary held by Hall, Whitney, and others. 



During the summer of 18T0 O. C. Marsh, professor of paleontology 



in Yale College, began a series of scientific expeditions into the western 



part of the United States, having for his primary object 



Sldkion^lsVo. tne collection of vertebrate fossil remains. The results 



of these expeditions soon placed Marsh among the 



leading vertebrate paleontologists of the world. 



