Baron Humboldt on Gas Springs. 279 



Avhich it is difficult to conceive, and which now serve as foun- 

 dations for the physical strength and the welfare of nations.* 

 Such beds are principally contained in basins, and are peculiar 



* In Lyell's interesting Travels in North America, ah'eady quoted, we 

 meet with the following remarks on the quantity of carbonic acid in the 

 .atmosphere, in which the plants of the coal formation flourished: — 

 " Before concluding the remarks, which are naturally suggested by a 

 visit to the Great Dismal, I shall say a few words on a popular doctrine, 

 favoured by some geologists, respecting an atmosphere highly charged 

 with carbonic acid, in which the coal plants are supposed to have 

 flourished. Some imagine the air to have been so full of choke damp 

 during the ancient era alluded to, that it was unfitted for the respiration 

 of warm-blooded quadrupeds and birds, or even reptiles, which require 

 a more rapid oxygenation of their blood than creatures lower in the scale 

 of organization, such as have alone been met with hitherto in the car- 

 boniferous and older strata. It is assumed, that an excess of oxj'gen 

 was set free when the plants which elaborated the coal subtracted many 

 hundred million tons of carbon from the carbonic acid gas which pre- 

 viously loaded the air. All this carbon was then permanently locked up 

 in the solid seams of coal, and the chemical composition of the earth's 

 atmosphere essentially altered. 



But they who reason thus are bound to inform us what may have 

 been the duration of the period in the course of which so much carbon 

 was secreted by the powers of vegetable life ; and, secondly, what 

 accession of fresh carbonic acid did the air receive in the same. We 

 know that, in the present state of the globe, the air is continually sup- 

 plied with carbonic acid from several sources, of which the three prin- 

 cipal axe, first, The daily putrefaction of dead animal and vegetable sub- 

 stances ; secondly, The disintegration of rocks charged with carbonic acid 

 and organic matter ; and, thirdly. The copious evolution of this gas from 

 mineral springs and the earth, especially in volcanic countries. By that 

 law, which causes two gases of different specific gravity, when brought 

 into contact, to become uniformly diffused and mutually absorbed 

 through the whole space which they occupy, the heavy carbonic acid 

 finds its way upwards through all parts of the atmosphere, and the solid 

 materials of large forests are given out from the earth in an invisible 

 form, or in bubbles rising through the water of springs. Peat mosses of 

 no slight depth, and covering thousands of square miles, are thus fed 

 with their mineral constituents, without materially deranging the con- 

 stituents of tlie ai;mosi)liere breathed by man. Thousands of trees grow 

 up, float down to the delta of the Mississippi and other rivers, and are 

 buried, and yet the air, at the end of many centuries, may be as much 

 impregnated with carbonic acid as before. 



Coral reefs are, year after year, growing in the ocean ; springs and 



