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lence of bone-ashes as a manure for wheat;and hence wheat succeeds best after clover, ifthe clover be fed off, but not if it be mowed *,as much of the phosphoric acid is communica*ted by the dung of animals.

The chief use of tartar vitriolate seems tobe, that it promotes the decomposition of wa-ter, as Mr. Senebier has observed t*

SECTION II.

OF THE CONSTITUTION OF FERTILE SOILS, AND THEMETHOD OF ESTIMATING THEIR FERTILITY.

The moft fertile soil is that which containsthe greatest quantity of the food of those ve-getables that nourish men and useful animals,and administers it to them with due economy.

The first essential requisite, therefore, to afruitful soil is, that it contain a sufficient quan-tity of the three or four simple earths abovementioned, and of the soluble carbonaceousprinciple. The other requisites are, that theproportion of each, and general texture of the

* 2d Young’s Annals, 36, 37.t Snr la Lumiere, p. 130.

E 2