of Lime used in Agriculture. 311 
Marshall’s account of the agriculture of the midland coun- 
ties, he speaks of the lime made at Breedon, near Derby, as 
destructive to vegetables, when used in large quantities. I 
therefore procured some pieces of it, and they were discovered 
to contain nearly the same proportion of magnesia as that be- 
fore described. In this quarry, the stone is frequently crystal- 
lized in a rhomboidal form; and petrified shells, not calcareous, 
but similar in composition to the stone itself, are sometimes, but 
very rarely, found in it. This substance seems to be common in 
Northumberland. In the third volume of the Annals of Agricul- 
ture, Dr. Fenwick, of Newcastle, observes, that the farmers of 
that country divide limes into hot and mild. The former of these 
is no doubt magnesian, as it has similar effects on the soil ; and 
he remarks, that it is not so easily dissolved in acids as the 
latter. At Matlock, in Derbyshire, the two kinds are contigu- 
ous to each other ; the rocks on the side of the river where the 
houses are built being magnesian, and on the other, calcareous. 
The magnesian rock appears also to be incumbent upon a cal- 
careous stratum ; for, in descending a cave formed in this rock, 
a distinct vein of common limestone may be observed, which 
contains no magnesia. The latter stratum is very full of shells ; 
but, though there are some also in the magnesian rock, yet 
they are very rare. In the following tables, containing the 
analysis of various specimens, some other places are mentioned 
where this substance is found, but of which I received no further 
information. 
After it was known that the magnesian marble and limestone 
consisted of the two earths, their proportion was attempted to 
be discovered, by trying how much gypsum and Epsom salt 
could be obtained, by means of vitriolic acid, from a certain 
S s 2 
