1800.] PUBLIC DOCUMENT— No. 4. 207 



stituents one from the other. In Ihe case of glacial soils, 

 however, for the reason that the division of the material is 

 accomplished mainly if not altogether by mechanical energ}^, 

 the resulting detritus is almost always composed of com- 

 pound bits ; that is, fragments having several minerals united 

 together. 



In ordinary glacial waste which has not been assorted 

 by the action of Avater, the proportion of the coarse com- 

 pound crystalline elements to the finely divided material 

 is commonly very great; generally, indeed, the pebbles of a 

 size to be visible to the naked eye constitute more than four- 

 fifths of the mass, and they frequently much exceed this pro- 

 portion. Not only was there an entire absence of vegetable 

 matter during the accumulation of the glacial waste on the 

 surface which it occupies, but the glacial waters were with- 

 out carbonic acid gas, and therefore the chemical work 

 accomplished during the ice term was small in quantity. 

 We may fairly term the detritus which the glacial period left 

 upon the surface an unnatural or pseudo-soil, — an earth 

 coating, which has in no way been reconciled with the needs 

 of vegetation ; while the ordinary soil coating produced 

 mainly by plant action constitutes the only real soil coating 

 of the earth. It is only when the detrital material left by 

 glacial action has become mixed with the vegetable waste, 

 and to the extent to which the commingling takes place, that 

 the material takes on a real soil character. 



Although the glacial soils are not immediately derived 

 from the subjacent rocks, but have always been more or less 

 aflected by transportative actions, there is in most cases a 

 certain relation ])etween nei2:hborino; rocks and the sheet of 

 glacial detritus from which the soil is evolved. Thus the 

 till or bowlder clay coating which is the commonest form of 

 glacial deposit is generally composed of materials which have 

 been derived from within five miles of the point now occu- 

 pied by the detritus. At any given place the commingled 

 clay, sand and pebbles usually represent something like an 

 average of the mineral character exhibited by the bed rocks 

 within that distance in the up-stream direction of glacial 

 flow. Even a cursory examination of the New England soils 

 will show the efiect of this principle of transportation. Thus 



