584 ADDITIONAL NOTES.

_imported into this country, and propagate their malady amonoft the native rats of this climate?

9. To be inferted at the end of Seët. X. 7. 8. p. 228.

Having now fpoken of carbon, of lime, and of clay, which with filiceous fand conftitute the principal ingredients of fertile foils, fome rules may be required for diftinguifhing the goodnefs of foils by the purchafer, as well as by the poffeflor. For this purpofe the chemical analyfis would firft prefent itfelf, as attempted by Fordyce, many years ago, and lately by Giobert, Bergmen, Kirwan, and others.

M. Giobert found, that one pound of a fertile foil in the vicinity of Turin contained of carbonic matter, which would burn and flame, about twenty-five grains, of flinty fand about 4400 grains, of clay about 600 grains, of lime about 400 grains, and laftly, of water about 7o grains. The fame author found that one pound of fome barren {oils was compofed of filiceous earth about 3000 grains, of argillace- ous eatth about 600 grains, and of calcareous earth about 400 grains, and I fuppofe without any carbonic matter.

Mr. Kirwan ingenioufly obferves, that the quantity of moifture, which fome countries are more liable to than others, fhould be nicely attended to, at the fame time that you eftimate the fertility of land by its analyfis, as moift climates or fituations may require more fand than drier ones; and therefore the fame component parts of foil would not be the moft fertile, on both the weftern and eaftern coafts of this ifland; as the former experiences more rain than the latter;

nor on the fummit, declivity, and bafe of moft mountains, which differ in their degree of moifture.

It appears from hence, that the chemical analyfis of foils is not yet arrived at fufficient accuracy to be depended upon with certanty to

difcover their degrees of fertility. But as the carbonic part of foil probably