13

■A DISCOURSE

Pigeons-dung consisted of a stiff glutinous matter, easily reducible todust of a grey colour, with some husky atoms, after dilution. Lastly,

The dung of poultry was so full of gravel, small stones, and sand, thatthere appeared little or no other substance, save a very small portion bothof white and blackish viscous matter twisted up together. This, of allothers, the most foetid and ill smelling.

These were all I had time and leisure to examine: I cannot say with allthe accuratenefs they were capable of, but sufficiently to encourage themore curious, and to satisfy myself, that the very finest earth and bestof moulds, however to appearance mixed with divers imperfect bodies,may, for ought we know, consist more of sandy particles than of anyother whatsoever, at least if from this criterion we may be allowed to pro-nounce what they seem to the eye, sands, crystals, or salts, call themwhat you please ; the consideration of which being so universally the cause

of vegetation, was no small inducement to me to see if, by examining theseveral earths, (though but by a cursory inspection) I might pofsibly de-tect what rudiments of such a principle there were lurking in them, ab-stractedly taken; not that I think earth to be salt alone, and nothingelse, (though perhaps little more besides sulphur) for so it produces novegetable that I know of, without water to difsolve and qualify it for in-sumption, and perhaps some other vegetable matter, fitted to manure andreceive the seeds, and keep the plant steady, which yet, for ought I candiscern, is also but a finer sort of sand, the clamminefs of it being rathersomething extrinsical and accidental to it, than any thing natural, andoriginally constitutive: for, the combination of these several mouldswhich gives the ligature, slipperinefs, and a diverfe temper, seems ratherto be caused by the perpetual and succefsive rotting of the grafs, plants,leaves, branches, mofs, &c. (than any peculiar or solitary principle apart)which, in long tract of time, has amafsed together a substance heteroge-neous to the ruder particles, which after the dilutions of the superficies(that is of the rich and fatter mould) appears to be little other than sand-,or fixed salts, of various figures and colours; since even the most obdu-rate and flinty pebble beaten and ground to powder, or by calcination re-duced to an impalpable dust, is as fine both to the eye, and smooth to thetouch, as the most smectic earths and marls themselves j such at least as