34 Causes and Course of Organic Evolution 



He says: "Regions of solfataric activity have always been 

 of peculiar interest to scientific observers, not only on account 

 of the curious and often extremely beautiful hot springs and 

 the rarer occurrence of geysers in such districts, but also from 

 the varied phenomena of rock decomposition and of mineral 

 formation and deposition which always accompany such hydro- 

 thermal action. It is in these natural laboratories that we 

 are permitted to see in operation processes which have pro- 

 duced important changes in the rocks of the earth's crust and 

 afford a key to many of the i)roblems of chemical geology. 



"There is perhaps no other district in the world where hydro- 

 thermal action is as prominent or as extensive as it is in the 

 Yellowstone National Park. In this area of about 3500 square 

 miles over 3600 hot springs and 100 geysers have been visited 

 and their features noted, and there are also almost innumerable 

 steam vents." 



As to general aspect and relation of the water, he says: "The 

 water of the Mammoth Hot Springs is remarkably clear and 

 transparent; the temperature varies at different springs from 

 80° F. to 165° F., exceeding 130° in all the larger springs. ^Yhile 

 hot, it generally possesses a sulphurous odor, the intensity 

 varying greatly at different springs, but always being strong 

 if the temperature exceeds 140°, when sulphur is found in- 

 crusting the Algse filaments groTvang near the vent of the spring. 

 When cold, the water is not peculiar in taste, or in odor, but 

 it is considered unfit for drinking, owing to the large amount 

 of carbonate of lime which it holds in solution." 



The comparative analyses given by him (on the opposite 

 page) are instructive : (Constituents grouped in probable com- 

 bination. Grammes per kilogram.) 



Now, in spite of the mdespread havoc to organisms that 

 volcanic and hot-spring activity often causes, we would still 

 insist that it is to regions that chemico-physically were similar 

 to water areas located in the midst of such hot-springs that 

 we have to look for organismal origin. In their waters all or 

 most of the elements are present that enter into organic com- 

 position; these elements show marked tendencies to colloid 

 organization; in. these waters also interaction of the different 

 types of colloid would have freest play. 



Most of the springs were bordered extensively ^\'ith colloid 

 siliceous deposits or "sinter." But in the northwestern corner 

 of the park the "Mammoth Hot Springs" were purely cal- 



