FACTORS OF AGRICULTURAL PRODUCTION 137 



permanent pasture. Pasturage in rotation with tillage, how- 

 ever, is quite another thing. As population increases, and with 

 it the necessity for economizing land, the importance of enlarg- 

 ing the tillable area will increase correspondingly. Therefore 

 the problem of clearing the land of stones and preparing it 

 for the plow, wherever that is economically possible, will be- 

 come a growing problem. 



Much of the work of clearing the land of stones, which has 

 been done hitherto, has been by the individual efforts of farmers 

 and by the simplest possible methods. The stones have been 

 lifted by hand, loaded onto a "stone boat," a sled, or a cart, 

 hauled away, and disposed of in the quickest manner possible. 

 This was a laborious method, suited to conditions where there 

 were small accumulations of capital, and where it was neces- 

 sary to clear only a small area of the less stony land. With the 

 growth of population, the increase of capital, and the improve- 

 ment of mechanical inventions, more effective methods may be 

 adopted. In the first place, there are uses for the stones which 

 are to be removed, in addition to that of building the time-honored 

 stone fence. Building and road materials are increasing in de- 

 mand, and, in some cases at least, it will be found economical to uti- 

 lize for other purposes the stones removed from the land in the 

 process of clearing it. Again, if the stones can be broken up and 

 reduced to a size too small to interfere with cultivation, they do 

 not need to be removed at all, but may better be left where they 

 are. Left in the soil, subject to the forces of decomposition, and 

 worn away by the friction involved in continuous cultivation, they 

 form a store of plant food which will be let loose gradually as it 

 is needed for the sustenance of crops. Portable crushing ma- 

 chines, driven by powerful engines, which will crush the stones 

 and leave them on the land, may be the means of increasing 

 the tillable area in the more densely populated sections where 

 land is becoming valuable. 



