Soil Session. 



Wednesday, January 10. 



KliS'i'ORING TPIE FERTILITY OF A RUN-DOWN FARM. 



(Dr. Ohas. E. Thorue, Director Ohio Experlmeut Station, Worcester, O.) 



I. 



yXstronomers tell us that the earth was once a red-hot, molten mass, 

 surrounded by an atmosphere in which the waters of its present seas were 

 vaporized, and which contained, as carbon dioxide, the carbon now found 

 in its beds of limestone and coal and in the vegetation covering its sur- 

 face. In time the surface of this mass had colored until a thin crust 

 had formed, and the vapor began to condense, at first into a boiling sea, 

 covering the entire surface, and overhung by a pall of cloud so dense 

 as to shut out the light. It was then that "the earth was without form 

 and void," for no land had appeared — "and darkness was upon the face 

 of the deep.'' 



With further cooling and consequent contraction of the interior mass 

 the crust was wrinkled and folded, being lifted into land areas in some 

 places and deepened into ocean basins in others. The seas were shallow 

 at first, and their waves beat upon their shores and ground them to sand, 

 as they are doing today, dissolving out of this sand the soluble portions. 



It is probable that the earliest living organisms were microscopic, 

 colorless, single celled plants, appearing in the barren, sandy beaches 

 of the primeval seas while the sun was still obscured, obtaining their 

 mineral food from the slowly dissolving sands, their carbon from the 

 heavily charged atmosphere circulating in the upper layers of the 

 sand, and their nitrogen from the same source ; plants similar in char- 

 acter to the bacteria which live under the surface of the soil today, some 

 of which undoubtedly still have the power of fixing free nitrogen, al- 

 though now they may obtain their carbon either directly from carbon 

 dioxide or from the accumulated organic matter of the soil, or indirectly 



A-7 



