358 Air. Henry on the Experiments made with 



taining^«;-^ fixed air. For the doftor had found 

 that plants, confined in pure fixed air, perilhed 

 fooner than in common air. 



I all along underftood your meaning to be, 

 not that fixed air, in a pure ftate, and quite 

 ftagnantj was nutritive to plants j but, that gra- 

 dually applied, and in a continued dream, while 

 the plant, at the fame time is not confined from 

 the common air, (in a manner analogous to what 

 may probably take place in nature) plants do 

 receive fuch a portion of nutriment, from the 

 fixed air, as is fuffici^nt for their temporary 

 fupport, even when removed from every other 

 means of receiving their food. This at lead 

 was the idea which I always entertained j and the 

 conclufion to be drawn from this theory is, that, 

 probably, fixed air conftitutes a part of the food 

 of plants, when growing in their proper element; 

 fuch air being difcharged by the different ma- 

 nures, which are mixed with their native foil; 

 and this theory, if juft, may lead to confiderable 

 improvements in agriculture. In the third 

 volume of Experiments and Obfervations on 

 different Kinds of Air, Dr. Piicftley at the fame 

 time that he acknowledges that '* he could con- 

 ^' ceive nothing more fair and decifive than your 

 *' experiments," yet declares himfclf convinced 

 that there muff have been feme fallacy in them, 

 and he feems to think that he had deteded it in 

 ?wo inftances. The firft fuppofed caufe of error 



was 



