REVIEW AND CONCLUSION. 375 
by the soil converted into, and retained in, a condition not 
of absolute, but of relative insolubility, and are kept avail- 
able to the plant by the continual circulation in the soil 
of the more abundant saline matters. 
“The soil (speaking in the widest sense) is then not only 
the ultimate exhaustless source of mineral (fixed) food, 
to vegetation, but it is the storehouse and conservatory 
of this food, protecting its own resources: from waste and 
from too rapid use, and converting the highly soluble 
matters of animal exuvie as well ag of artificial refuse 
(manures) into permanent supplies.”’* 
By absorption as well as by nitrification the soil acts 
therefore to prepare the food of the plant, and to present 
it in due kind and quantity. 
* The author quotes here the concluding paragraphs of an article by him ‘On 
Some points of Agricultural Science,” from the American Journal of Science and 
Arts, May, 1859, (p. 85). which have historic interest in being, so far as he is 
aware, the earliest, broad and accurate generalization on record, of the facts of 
soil-absorption. 
NOTICE TO TEACHERS. 
At the Author’s request, Mr. Louis Stadtmuller, of New Haven, 
Conn., will undertake to furnish collections of the minerals and rocks 
which chiefly compose soils (see pp. 108-122), suitable for study and 
illustration, as also the apparatus and materials needful for the chemical 
experiments described in ‘‘ How Crops Grow." 
