APPENDIX—GEOLOGICAL SURVEY. 
437 
We would like to know—and it is important that we should 
know—how the water obtained the silica from which these 
crystals were formed. Was it dissolved out of disintegrating 
rocks above, and brought in solution in rivers and streams that 
emptied themselves into the primeval ocean ; or did the free 
elements of silica, like certain other elementary substances, 
rise in gaseous emanations with escaping heat from below, and 
becoming subsequently condensed in the fissures, find their 
way in thermal waters to the ocean above, where entering into 
chemical combinations they were deposited in the form of 
small crystals as we find them? 
Suppose Iceland should be submerged to a considerable 
depth beneath the ocean, and those plains, situated about thirty 
miles froifi that noted volcano, Hecla, now full of hot springs, 
steaming fissures and boiling geysers whose waters hold a large 
amount of silica in solution, 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 ? 
In studying either the sandstone or limestone formations that 
underlie the lead district, we do well always to remember their 
very great antiquity ; and also the fact that very different phys¬ 
ical conditions prevailed then from what we find now. If we 
look to my large map, we see the Potsdam sandstone—to 
which the layer that I have just been describing evidently be¬ 
longs, although separated from it by over two hundred feet of 
limestone—is spread out over the upturned ridges of the azoic 
rocks, traversed as we know them to be where they become 
the surface rock with various faults and fissures and chimney¬ 
like perforations. This formation, according to the opinion of 
scientific men, belongs to the most ancient of the strata which 
form the crust of the earth, and was formed prior to the intro¬ 
duction of animal or vegetable life on our planet; from which 
it is inferred that the temperature of our planet at that time 
was too h ; gh to admit of organic life. If the absence of vege¬ 
table and animal life at that period be an evidence that the 
temperature was too high to admit of it, then the formation of 
