174 THE LURE OF THE LAND 



candescent gas was incandescent liquid, which came in 

 due season as time rolled by. Finally, by the further 

 process of cooling, a crust was formed upon the surface 

 of these liquids which was the beginning of the solid 

 surface of the earth. This crust would naturally be 

 of the same composition as the liquid matter from 

 which it was formed practically homogeneous in 

 character and consisting of the mineral matters only 

 which could exist in a solid state at that temperature. 

 " Whether the above theory relating to the life history 

 of the planet up to the formation of igneous rock is 

 true or not is of little consequence in so far as the 

 genesis of the soil is concerned. It is certain that 

 the mineral parts of soil are derived from rocks. We 

 may not know how these rocks originated. 



THE EVOLUTION OF THE SOIL. 



" In speaking of the soils of the United States, I 

 would like to trace briefly their evolution from this 

 primeval crust, which was the first ice formed on this 

 globe. What have been some of the more active forces 

 which have broken up this congealed mineral matter and 

 brought it into the present condition in which we see 

 the surface of our globe ? First of all the action of 

 water, which is and has been one of the chief disinte- 

 grating agents upon the earth's surface. At the time 

 the first crust was formed over the surface of the earth 

 all the water which now exists must evidently have 

 been above the earth's surface in the form of steam. 

 As the cooling slowly progressed this steam tended to 

 condense in the form of clouds and finally water. 

 Thus the original rain falling upon the hot surface of 

 the earth was at once converted again into steam, but 

 not until it had started a certain solvent action. Water 



