STATE HORTICULTURAL SOCIETY. 83 



act directly upon it, and consequently it has little or nothing to do in 

 determining the character of the prairie soils. Usually, the prairie soil 

 rests upon a tenaceous brown clay subsoil, that seems to differ from the 

 soil itself only in color, and although resting directly upon the gravellv 

 clays of the drift, is itself quite free from gravel, and therefore would 

 seem to have a different origin from the true drift. Whether this clay 

 has been formed on the spot, by the growth and agency of a peculiar aquatic 

 vegetation, as explained by Prof. Lesquereux, in his chapter on the 

 "Origin and Formation of the Prairies," is a point that perhaps is not 

 fully settled ; but as it is, on the whole, the most plausible explanation 

 that I have seen of the origin of the soil and subsoil of the prairies, I will 

 beg your indulgence while I briefly state it in this connection. It is a 

 generally admitted fact that, during the latter part of the glacial epoch, 

 nearly the whole area of the Western States, north of the Ohio river, was 

 beneath the water, and during the emergence of this wide area there 

 must have been a period when the surface was covered with shallow lakes 

 and ponds ; and during this period the finely comminuted clay that 

 forms the soil and subsoil of the prairies was deposited in the following 

 manner, to quote the author's own words : 



" In stagnant water, whenever shallow enough to admit the trans- 

 mission of light and air in sufficient quantity to sustain vegetable life, the 

 bottom is first invaded by conferva, and especially by characece, and a 

 peculiar kind of floating moss, technically known as Hypnum aduncum. 

 These plants contain in their tissues a great proportion of lime, alumina, 

 silica, and even oxide of iron, the elements of clay. Morover, this vege- 

 tation of the low stagnant waters feeds a prodigious number of small 

 moUusks and infusoria, whose shells and detritus greatly add to the 

 deposits. The final result of the decomposition of the whole of this 

 organic matter is that fine clay of the subsoil of the prairies, which is 

 truly impalpable when dried and pulverized and unmixed with sand. In 

 the lakes of the high prairies, the phenomena sometimes present a pecu- 

 liar character. At the depth of from one to three feet, the above-namd 

 plants, mosses, confervte and charas form a thick carpet, which hardens, 

 becomes consistent like a kind of felt, and, floating about six inches above 

 the bottom, is nearly strong enough to sustain the weight of a man. This 

 carpet is pierced with holes, where fish pass to and fro, and the bottom 

 under it is that fine impalpable clay, evidently a residue of the decompo- 

 sition of its plants. At the depth of three and a half to four feet, this 

 vegetation suddenly ceases, and the bottom is pure sand, with pebbles and 

 shells. Near to the borders, on the contrary, at a depth of one foot, 

 the carpet of mosses, etc., begins to be intermixed with sedges, which 

 become more and more abundant in proportion as the depth decreases. 

 As soon as the blades of these plants reach above the water, they absorb 

 and decompose carbonic acid, transform it into woody matter under 

 atmospheric influences, and then their detritus is at first clay mould, and 

 then the pure black mould of the prairies." . 



I have only quoted some of the salient points made by the author, 

 in discussing this subject ; and those who would like to consult his views 



