234 SUMMARY OF THE METHOD OF EXAMINATION. 



with half a wine-glass full of spirit of salt, and frequently stirred, 

 ^''hen minute bubbles of air cease to rise from the soil on settling, this 

 p'ocess may be considered as at an end. The loss by this treatment 

 will be a little more than the true per centage of lime,* and it will gen- 

 erally be nearer I he truth if that portion of soil be employed which has 

 been previously heated lo redness. 



4°. A fresh portion of the soil, perhaps 200 grs. in its moist State, may 

 now be taken and washed to determine ihe (]uantity of siliceous sand it 

 contains. If the residual sand be supposed to contain calcareous matter 

 its amount may readily be determined by treating the dried sand with 

 diluted muriatic acid, in the same way as when determining the whole 

 amount of lime (3°.) contained in the unwashed soil.f 



Let me illustrate this by an example. 



Example. — Along the outcrop of some of the upper beds of the green 

 sand in Berkshire, Wiltshire, and Hampshire, and probably also in 

 Buckingham and Bedford, occur patches of a loose friable grey soil 

 mixed with occasional fragments of flint, which is noted for producing 

 excellent crops of wheat every other year. It is known in the valley of 

 Kingsclere, at Wantage, and Newbury. I select a portion of this soil 

 from the latter locality for my present illustration. 



1°. After being dried in the air, and by keeping some time in paper, it 

 was exposed for some hours to a temperature sufficient to give the white 

 paper below it a scarcely perceptible tinge : by this process 104^ grs. 

 lost 4 grs. 



2°. When thus dried, it was heated to dull redness. It first black- 

 ened, and then gradually assumed a pale brick colour, the change, of 

 course, beginning at the edges. The loss by this process was 4^ grs. 



3°. After this heating, it was put into half a pint of pure rain water 

 with half a wine-glass full of spirit of salt. After some hours, when the 

 action had ceased, the soil was washed and dried again at a dull red 

 heat. The loss amounted to 3 grs. 



The soil, therefore, contained 



Water 4 grs. 



Organic matter (less than) . . 4^ 

 Carbonate of lime (less than) 



Clay and sand 93 



4°. By boiling and washing with water, 291 grs. of the undried soil 

 left 202^ grs. of very fine sand chiefly siliceous, — 104i, therefore, would 

 have left 73 grs., or the soil contained per cent. — 



* A more rigrorous method, of determining the lime when less than 5 per cent, will be 

 given in the following lecture. 



* The weighings for the purposes here described may be made in a small balance with 

 grain weights, sold by the druggists for 5s. or 6s., and the vegetable matter may be burned 

 away on a slip of sheet iron or in an untinned iron table-spoon over a bright cinder or char- 

 coal fire— care being taken that no scale of oxide, which may be formed on the iron, be al- 

 lowed to mix with the soil when cold, and thus to increase its weight. Those who are in- 

 clined to pert'orm the latter operation more neatly, may obtain for about 6s. each — from the 

 dealers in chemical apparatus — fiin light platinum capsules from 1 to IX inches in diame- 

 ter, capable of holding 100 grs. r'.:' soil— and for a few shillings more a spirit lamp, over 

 which tlie vegetable matter of thi soil may je burned away. With care, one of these little 

 capsules will serve a life-time. 



