CH. II.] THE ROOTS. 65 



Much injury is done by raking the surface so very 

 much. It is not only the means of binding and 

 cakincf the surface, but it clears the stones o£f as well'". 

 The eaith, in its natui'al state, has stones, &c., to 

 keep it open and porous, &c. If the earth be 

 sufficiently di'ained, either naturally or othei-wise, ' 

 and the surface kept open, there is no fear of suffer- 

 ing either from drought or moistui'e." 



Exposing the soil in ridges during the winter is 

 usually practised by gai'deners for the pui'pose of 

 destroying predatory vermin, but it is also beneficial 

 by aiding the atmosphere to pen-ade its texture, 

 which textui'e is also rendered much more friable 

 by the frost. M. Schluber says that freezing re- 

 duces the consistency of soils most remarkably, and 

 that in the case of clays and other adhesive soils, 

 the diminution of this consistency amounts to at 

 least 50 per cent. In hoeing clay he found it re- 

 duced from sixty-nine to forty-five of the scale already 

 stated, and in the ordinary arable soil from thirty- 

 three to twenty. He satisfactorily explains this 

 phenomenon, by obsendng that the crystals of ice 

 pervading the entire substance of the frozen soil 

 necessarily separate the particles of earth, rendering 

 their points of contact fewer. 



We have seen that plants seai'ch after and acquire 



* A finely pulverized even surface cakes after rain much more 

 than a surface rather rough. 



F 



