580. OF QUAC KE IME

Thefe very hard kinds of marle may be ealily burnt into lime, fo that they may be indifferently called marle or lime-ftone.

3d, The fame may be faid of the diftinc- tion between marle and chalk(§ 5, p. 402) Many fubftances which have the appear- ance and diftinguifhing properties of chalk, contain clay in different proportions.— Thefe diffolve in the air, or rum, as it is termed, more readily than the pure hard kinds of chalk, and feel more unétuous or fatty to the touch; from whence they are

alled fat chalks.—Thefe, however, may be converted into lime;; fo that they might indifferently be called chalk, marle, or lime-

The lime that is made from any of thofe fubftances that contain clay in their com- pofition, is more proper for manure than for

cement;—efpecially that made from thofe

pe fubftances that may be made to /a// after they have undergone only a fm all degree of

leat in— them, as in chalk; be-> caufe, in thefe cafes, the clay will not be fufficiently burnt to prevent it from being affected by water, and rendered foft by it.

The proportion of clay and fand contain-

ed