7 6

the acid boil; afterwards let it evaporate nearlyto dryness: when cold, pour on it graduallysix or eight times its weight of distilled water,and, after some hours, pour off the solution ona filtre; the filtre should previously be weighed,and its edges soaked in melted tallow*; thesubstance found on the filtre being weighed(subtracting the weight of the filtre) gives thequantity of silicious matter; and this weightsubtracted from that of the dried mass, givesthat of the argill. In this case I will supposethe silicious mass to weigh 140 grains, then theargillaceous should weigh ,95 grains.

Then the composition of one pound of the

soil is as follows :

Stony matter - 1017,66

Water - - 100

Fibres of roots - 10

Soluble coal - 12

Saline matter - 4

Silex 140x12 = 1680Argill 95 X 12 = 1140Mild calx 150 X 12 = 1800

5763,66f

* An ingenious contrivance of Dr. Black,t An error of 3,66 grains for decimals omitted insubtractions.