18 



A DISCOURSE 



Pigeons'-duiig consisted of a stiff, glutinous matter, easily reducible to 

 dust of a gray colour, with some husky atoms, after dilution. Lastly, 



The dung of poultry was so full of gravel, small stones, and sand, that 

 there appeared little or no other substance, save a very small portion botli 

 of white and blackish viscous matter twisted up together. This, of all 

 others, the most foetid and ill smelling. 



These were all I had time and leisure to examine : I cannot say with aU 

 the accurateness they were capable of, but sufficiently to encourage the 

 more curious, and to satisfy myself, that the very finest earth and best 

 of moulds, however to appearance mixed with divers imperfect bodies, 

 may, for ought we know, consist more of sandy particles than of any 

 other 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 them 

 what you please; the consideration of which being so universally the cause 

 of vegetation, was no small inducement to me to see if, by examining the 

 several earths, (though but by a cursory inspection,) I might possibly 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 nothing 

 else, (though perhaps little more besides sulphur,) for so it produces no 

 vegetable that I know of, without water to dissolve and qualify it for in- 

 sumption, and perhaps some other vegetable matter, fitted to manure and 

 receive the seeds, and keep the plant steady, which yet, for ought I can 

 discern, is also but a finer sort of sand, the clamminess of it being rather 

 something extrinsical and accidental to it, than any thing natural, and 

 originally constitutive : for, the combination of these several moulds 

 which gives the ligature, slipperiness, and a diverse temper, seems rather 

 to be caused by the perpetual and successive rotting of the grass, plants, 

 leaves, branches, moss, &c. (than any peculiar or solitary principle apart) 

 which, in long tract of time, has amassed 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 the 

 touch, as the most smetic earths and marls themselves; such at least as 



