ij;o To the Agricultural Society, 



and knolls were fupported, whofe wafte by the wafh of rains 

 are continually great ; . yet their fpontaneous produ£lions, or 

 when well cultivated, were equal to that of level land. To 

 fuppofe that they derive their fupply wholly from the earth, 

 as was the general received opinion, appeared aninconfiftency; 

 for the fubflances that compofe vegetable Hfe are of a fubtle 

 fluid, and of a refined volatile nature, and of confequence the 

 fubterraneous heats will always keep the volatile falts near the 

 furface of the earth ; therefore, they mufl derive their fupply 

 from fome other quarter, which might be accounted for after 

 the following; manner : — Low and level lands receive all the 

 wafh, and of confequence a fermentation will frequently take 

 place, from the different compounds that are collected ; or 

 when that is not the cafe, the ftrife or agitation that exifl:s 

 throughout nature, to keep up an equilibrium, will caufe an , 

 effluvium to fly from thofe bodies. Thcfe effluvia, when 

 taking their flight with the air, from the advantageous 

 fituation of the hills, a^greater quantity or bpdy of them will 

 ftrike or light upon it, if it is covered with trees, clover, or 

 other vegetables, or the ground prepared ; the pores of 

 vegetables, or the cavities that are between each particle of 

 earth, will receive them, fhould they light on ground already 

 charged, or on an impenetrable body; it will take its flight 

 as the heat increafes, and when there is not a fuflicient 

 quantity of moiflened or .penetrable bodies to receive them, 

 they will i^r^-^nme ncflilential to the human fpecies, as wc have 



