of Lime used in Agriculture . 313 
ments, the spar was left in the solution till it suffered no further 
diminution. For this purpose, it was necessary' to keep them 
slightly warm for some days, during which time, the phials 
were generally closed, to prevent any escape of the acid. 
The first experiment in the following table was made upon 
known quantities of magnesia and calcareous earth, to try the 
accuracy of the process. For this purpose, also, the second 
was repeated upon a piece of limestone, previously powdered, 
to render every part of it of the same quality. The first column 
shews the quantity of calcareous spar which might have been 
dissolved by the acid required to take up the magnesia. The 
second shews the corresponding quantities of magnesia in 25 
grains of each substance. The third expresses the quantity of 
lime. This was inferred by subtracting the weight of the mag- 
nesia, and of the iron and clay, from 13.2 grains, the weight of 
the whole quantity of earth in 25 grains of limestone. This is- 
probably not very incorrect, as, in two specimens which differed 
most in the proportion of magnesia and lime, the weight of the 
two earths was nearly the same. 
A piece of Dolomite, from Rome, was wrapped in a thin leaf 
of platina, that no part of it might be lost, and, being then ex- 
posed to a strong heat, left of earth - 52.9 per cent. 
Dolomite from Mount Vesuvius - 52.8 
Breedon limestone - -• - 52.4 
Calcareous spar left of lime - - 55.8 
In three of the experiments, also, the calcareous earth was 
precipitated by mineral alkali-; and the quantity of it being 
tried by that of the marine acid required to dissolve it, it cor- 
responded very nearly with that put down. 
A quantity of marine acid which would dissolve 15 grains of 
calcareous spar, would also dissolve 5.5 of calcined magnesia, and . 
