CLIMATE AND CARBONIC ACID. 249 



Among the rocks of any range there are youngest strata that mark a 

 date earlier than the most remote at which the uplift may have 

 occurred. Impressed with the magnitude and grandeur of mountains, 

 geologists assigned them an antiquity limited only by the age of their 

 component strata, but through the interpretation of landscape forms 

 evidence is now accumulating to show that existing ranges are, as a 

 rule, comparatively young. One interesting conclusion is that we live 

 at a time near the culmination of an epoch of mountain growth, that 

 mountains are now widely distributed and high as compared with 

 those of many preceding periods, and the earth's activity as thus 

 manifested is not materially less now than formerly within known 

 geologic history. The crustal adjustment which produced existing 

 mountain ranges and expanded continents appears to have culminated 

 just before or very early in the Glacial epoch, and the recognition of 

 this fact was the principal basis for the hypothesis that glaciation was 

 related directly to elevation of the land areas. Chamberlin interprets 

 the relation through the influence of rock-weathering upon the carbon 

 dioxide of the air, and attributes the cold period to the resulting 

 thermal transparency of the atmosphere. 



The carbon dioxide abstracted from the air by weathering passes 

 into the aqueous circulation of the globe, one-half of it in combination 

 as monocarbonates, the other half superadded to form bicarbonates. A 

 further step in framing the hypothesis is to follow this second part 

 until it shall be returned to the air, which shall thus be reenriched 

 and may promote a period of mild climate. 



The ocean is a great reservoir holding carbon dioxide in combina- 

 tion with various bases as bicarbonate. It contains also many other 

 salts. Assuming that all the solids dissolved in sea-water have been 

 derived from the land at a rate of solution equal to that now deter- 

 mined by analyses of river waters, it is possible to make a curious calcu- 

 lation, which shows that the carbonate of lime now in the sea would 

 have accumulated in 60,000 years, whereas the common salt, chloride 

 of sodium, would have required 166,000,000 years. The common salt 

 is not removed from solution, nor is there reason to suppose that there 

 is any special source from which it is concentrated, but which does 

 not supply lime; it may, therefore, be taken as a standard of com- 

 parison, which shows that there is much less lime in the sea than we 

 should expect. The deficit is accounted for by the great beds of lime- 

 stone deposited from the sea at various periods from the long past to 

 the present. 



In the ocean, bicarbonate of lime is dissolved in a proportion less 

 than that which the waters can hold in solution, and, according to the 

 principles of the older chemistry, it is under these conditions a fixed 

 combination, which remains dissolved. Should, however, the mono- 



