158 AIR AND LIFE. 



and extent of such masses of organic remains. All know that in every 

 geological formation calcareous strata of great thickness are found, 

 which are merely agglomerations of skeletons, and Van Dechen has 

 endeavored to form some idea of the quantity of carbonic acid which 

 may be contained in such strata. The result is very striking. He comes 

 to the conclusion that in the lime strata of the Carboniferous epoch alone 

 there is an amount of carbonic acid imprisoned which is six times more 

 considerable than that at present contained in the whole atmosphere. 

 The problem has been carried further by Sterry Hunt. Taking this 

 result into consideration, and forming an estimate of the whole quantity 

 of carbonic acid combined with lime in the whole geological series, he 

 finds that the amount of carbonic acid thus imprisoned in the calcareous 

 rocks would, if entirely liberated, form an atmosphere two hundred times 

 more considerable than that which at present surrounds the planet. In 

 such a case the pressure would be so much increased that the gas would 

 necessarily become liquid. The inference which he draws (Brit. Asso- 

 ciation for the Adv. of Science, 1878) is that the enormous amount of 

 carbonic acid at present stored in the depths of geological strata has 

 never been simultaneously, even for a short time, present in the atmos- 

 phere, but that it must have reached the latter in small quantities and 

 gradually. Mr. Sterry Hunt is of opinion that all this carbonic acid 

 has come to our planet from celestial regions in the course of hundreds 

 of centuries. Whatever may be thought of this interpretation as to the 

 origin of the gas, one fact remains unassailable, and that is the enormous 

 quantity of the latter stored up in the earth's crust; and if in the course 

 of time organisms have been able to accumulate such a provision and 

 are still operating as they undoubtedly are under our very eyes, we cer- 

 tainly can not help coming to the conclusion that we have here one of 

 the most important agencies by means of which the atmosphere is being 

 unceasingly kept sufficiently pure for maintaining life. 



Lastly, come the oceaus. Few are aware that the salt waters play a 

 most interesting and important part in the general regulation of the 

 atmosphere, and are one of the agencies which by absorbing carbonic 

 acid prevent it from overaccumulating in the air. Mr. Schloesing's 

 remarkable investigations have shown that the seas contain a large 

 amount of dissolved carbonic acid, a much larger amount, in fact, than 

 is to be found in the whole atmosphere. The equilibrium is preserved 

 as follows : When carbon dioxide becomes more abundant than usual in 

 air, in consequence of an increased production of this gas, and no com- 

 pensatory destruction or withdrawal is effected by plants or animals, 

 part of it dissolves in the salt waters, and combines with the insoluble 

 and neutral carbonate of lime, always present there, producing a soluble 

 bicarbonate of lime which dissolves immediately, and, inversely, if the 

 amount of carbonic acid in the atmosphere decreases, the soluble bicar- 

 bonate is decomposed into carbonic acid, which is set free and diffuses 



