Investigations and Writings of Baron Humboldt. 209 
tive evaporation filled the atmosphere with vapours of the 
most varied description. In this .way it exercised’a much 
greater pressure on the closely covered solution than pre- 
viously, and hindered its rapid vaporisation; the solution 
must have acquired a greater heat ere new precipitates could 
be produced, and the separation of its constituents must have 
taken place more slowly. By this supposition was explained, 
in avery ingenious manner, the highly crystalline condition of 
the older rocks, which were formed at a lower temperature, 
and the more earthy, imperfectly crystalline aspect of all 
newer formations, which were separated more rapidly at a 
higher temperature. The heat arising from these events 
must for some time have produced, at all parts of the earth’s 
surface, a climate similar to a tropical one, which disappeared 
so soon as the heat developed was lost by radiation and dis- 
persion in space, and remained only for that portion of the 
surface in which the position of the sun rendered possible the 
continuance of a considerable development of heat. 
This able view has this great advantage, that we do not 
require, as in those mentioned above, to introduce violent 
means for explaining the phenomena. Farther, it agrees 
extremely well with the known laws of the phenomena of 
nature, as these are exhibited in fluid bodies when they pass 
into the solid state; and this is certainly a great recommenda- 
tion. However, we can, by a general consideration of the 
phenomena presented by nature, very easily convince our- 
selves that it is not sufficient as an explanation in the manner 
just described. It is certain that the greater portion of the 
deposits which resulted from the general mass of water at the 
different periods of the formation of the crust of the earth, 
and which furnished the stratified rocks, were more of a me- 
chanical than a chemical nature. The immensely extensive 
formations of sandstone and conglomerate are composed of 
parts which were formerly suspended and not dissolved in the 
water. The masses of clay belonging to them, the clayslates, 
the slate clays of the coal formation, the slaty clays of the 
newer sandstones, are evidently chiefly the result of the de- 
struction of the previously existing very felspathic older rocks, 
which, by decomposition, are partially converted into masses of 
