280 ANALYSES OF SOILS. 



The green shales, or rock from which the above soils were derived, is composed as 

 follows : 



Water of. absorption 0*50 



Organic matter 6-00 



Silicates 34'56 



Carbonate of lime 50 -OS 



Carbonate of magnesia 2. 16 



Peroxide of iron and alumina 6- 38 



99-66 



The inorganic salts, the sulphates of lime and magnesia, and chloride of sodium, exist 

 also in the rock, but the proportion was not determined. 



The composition of the rock is eminently fitted to sustain a soil in constant fertility. 

 The upper surface of the rock, when near the top of the ground, is easily broken up by 

 the plow ; and its debris, being mixed with the old soil, becomes speedily a fit material 

 for sustaining a vigorous growth of the cultivated vegetables. 



It is a fact worthy of a passing notice, that although gypsum abounds in the midst of the 

 shales which underlie Onondaga and Cayuga counties, still it is not only wanting in the 

 soil as a general rule, but is required in the practice of husbandry, and seems to produce 

 effects as beneficial as in any other part of the country where it is unknown among the 

 formations. This may arise partly from its solubility : it may be removed rapidly from 

 the soil by solution. If this is true, it is evident that there is no danger to be apprehended 

 from an accumulation of it in the soil by the ordinary use of it. Another reason why 

 plaster is not found abundantly in the soil, is its change of constitution, or its change from 

 a sulphate of lime to a carbonate, by means of the carbonate of ammonia contained in the 

 atmosphere. This change seems to be indicated by a few experiments which have been 

 made during the last five years. 



The debris about the beds of plaster consists mainly of carbonate of lime, largely mixed 

 with clay in which it woidd seem that sulphate of lime must have existed originally. 

 Thus the debris of the plaster beds from Cayuga bridge, I found composed as follows : 



Water of absorption 4-88 



Organic matter B-OO 



Silicates 41 -75 



Peroxide of iron and alumina 8*88 



Carbonate of lime 22*20 



Carbonate of magnesia 19"30 



100-01 



As the debris about these beds is often rich in magnesia and carbonate of lime in a sfate of 

 minute division, there is no doubt l)ut the material will be as useful, applied to land, as 

 the plaster itself; besides, it is not necessary that it should be transported to a plaster mill, 

 as it undergoes disintegration, and becomes in a few years sufficiently fine for use. 



