MATERIALS EXISTING IN WATER. 4 1 



senes as the means by which they procure certain mineral 

 matters no less indispensable to their development. These 

 matters are not to be discovered in the atmosphere or in rain 

 water, but exist in the rocks of which the ground on which 

 Avc tread is composed, and which, broken into fragments of 

 various sizes, from the finest dust to the stone that turns the 

 plough aside, and, mixed with the decaying remains of the 

 weeds or crops that have grown upon them, constitute the 

 arable soil of the fai'mer. It is the carrying out of certain 

 plans to enable plants in the readiest manner to supply them- 

 selves with the materials for their support which are stored 

 in the soil that gives employment to the industrious labourer, 

 and that requires both practice and science on the part of 

 him who has the management of the work. 



