132 Literary and Philosophical Society, 



some plants, with the moisture that enters their roots, is 

 far from being improbable. But that whole provinces can 

 even be covered over with it, or that it can be generated in 

 these organised bodies, as Lemeri and some others have 

 imagined, must exceed all belief. 



' The accounts which travellers generally give us of 

 this salt are, that it is extracted from the soil of the 

 countries they have visited, by elixiviating it with water, and 

 evaporating the fluid ; which we believe may be consistent 

 with truth ; but here it should not be forgotten that a 

 certain portion of wood-ashes is always added to this soil 

 before it is elixiviated, a circumstance which, either through 

 ignorance or inattention, they have too often omitted to 

 mention.' 



P. 190. * Of these earths the most distinguished are, the 

 rubbish of old houses, the ruins of old vaults and cellars, &c., 

 which rarely fail to yield us the crystals of this salt when 

 elixiviated with wood-ashes. That these earths possess an 

 acid quality is not to be disputed ; seeing that upon re- 

 ducing them to a coarse powder, and percolating a fixed 

 alkaline solution through them, this solution will be neutral- 

 ised, and no longer yield us an alkaline, but a neutral 

 salt' 



P. 191. 'From the well-known fact, that the rubbish of 

 all such houses as have been occupied by the filthiest in- 

 habitants^ and of such clay walls as have stood in the neigh- 

 bourhood of dunghills, or wherever putrid vapours more 

 plentifully abound, is always most strongly impregnated 

 with this acid, it is most natural to believe, that these vapours 

 must confer it upon them, and consequently, that it must 



