RESTOCKING OS ROCKY MOUNTAINS. 313 



CHAPTEK VII. 



RESTOCKING MOUNTAINS HAVING ROCKY SURFACES. 



Nothing can be grown on rocks that are entirely bare 

 except some varieties of mosses and plants of the lowest 

 order which derive their food wholly from the air, and 

 use the rocks only as a holdfast. But, when the sur- 

 face of the rock has been broken up by the action, both 

 of the rock-devouring bacilli* and the elements — heat 

 and cold principally;— and crumbled into its original 

 composing parts, the growth of plants and trees may take 

 place. This process is still going on all over the earth, 



*Very interesting observations in regard to the decomposition of 

 rocky mountains and the formation of humus upon their surface have 

 been lately made by Professor A. Muentz. He found that the contin- 

 uous dissolution of uncovered rocks was not caused solely by the 

 chemical and mechanical action of the atmosphere ; but also in part 

 by some microbes which develop in pm-e mineral solutions by obtain- 

 ing the required carbon from the carbonic acid and carbonate of 

 ammonia contained in the atmosphere. These minutest of animal- 

 cules penetrate into the smallest, and, to the naked eye, imperceptible 

 fissm'es of roclss, manifesting their presence by leaTing behind them 

 atoms of organic substances which serve to form the first traces of 

 humus. During the winter they rest and take their winter nap ; but 

 when the warm season returns, they resume then- rock-destroying 

 activity and enter deeper and deeper into the solid stone formation. 

 While the geologist stands here full of admiration at the results of the 

 workings of nearly invisible microscopic creatures, entirely unknown 

 up to the present lime ; the physiologist is still more astonished at the 

 ability of these bacilli to build up their substance by assimilating 

 carbonic acid and ammonia without the help of any other power but 

 the warmth generated by tlie oxydation of ammonia. Undoubtedly 

 these microbes have exercised a great influence upon the present con- 

 tour of our globe, and the accumulation of the plant-nourishing 

 humus ; they will continue their action upon the stone foi-mation of 

 our planet till the last rock has crumbled to pieces. 



