DECEMBER MEETING. 



303 



These arc tonued earthy matters, to distinguish them from those matters 

 which are derived from the atmosphere. 



If a soil is formed by the mechanical disintegration of one kind of rock, it 

 will contain all of the elements of that rock, and no more. If that rock is 

 Biagnesian limestone, it will have an abundance of lime and magnesia, but 

 would not contain a sufficient quantity of the other earthy ingredients of plants 

 to make a fertile soil. If we mix with this the soil from disintegrated sand- 

 stone, we add silicic acid, and if it is highly impregnated with iron and manga- 

 nese, as most sandstones are, we should have a sufficient quantity of those ele- 

 ments also. If we mix with this plaster rock and lime rock, containing large 

 quantities of fossil shells and bones, sulphuric and phosphoric acids will be sup- 

 plied. Granite added will give us an abundance of potash from its feldspar 

 and mica. Add to this material derived from a salt formation, and we have 

 chlorine and soda ; though this is not material, as these elements usually exist 

 in the other rocks named in sufficient quantity for all agricultural purposes. A 

 soil thus formed would have all the earthy elements which enter into the compo- 

 sition of plants. But a soil containing these properties, or earthy matters alone, 

 no matter in what proportion, would not be, without the addition of otlier mat- 

 ter, a very fertile soil. It must have other substances which, althougli they do 

 not enter directly into the composition of plants from the soil yet act as agents 

 in the process of separating these elements from the soil, and preparing them 

 for absorption by the roots of plants. The principal of these other matters are 

 alumina, carbonic acid and vegetable mould. The two first would be amply 

 supplied by the lime and granite rocks; the latter must be supplied by decayed 

 vegetation. 



It matters but little in what proportion these elements exist, providing there 

 is a sufficiency of each to fully supply the demands of successive crops, and the 

 silica (common sand) so far predominates as to make a porous and friable soil. 

 A soil mtiy be composed of seventy-five per cent, of silicious sand and yet be 

 fertile, if these other elements are there in sufficient amount. Pulverizing and 

 mixing together these rocks, with the addition of from three to five per cent, 

 of vegetable mould, would make a soil rich enough for all practical })urposes, 

 without the application of special manures, and without danger of early "wear- 

 ing out.'' 



The surface of this country is covered to a great depth with what geologists 

 term drift, a mass of earth which has been formed by the breaking up and 

 grinding together of rocky masses by glacial action, until they have become 

 pulverized and mingled togetlier into a more or less homogeneous mass of sand, 

 clay, gravel, and boulders. 



The rocks from which chis drift is derived are those which out-crop between 

 the noi'thern terminus of the Lower Peninsula and the southern shore of Lake 

 Superior. These rocks or geological formations, commencing at the mouth of 

 Grand Traverse Bay and going north-northwest in the direction from which 



