VOL. LXXIV.] PHILOSOPHICAL TRANSACTIONS. 501 



ference, that it suffers some of its dephlogisticated air to escape, while it remains 

 united to the alkali itself, in the form of phlogisticated nitrous acid. As to the 

 production of dephlogisticated air from plants, it may be said, that vegetable 

 substances consist chiefly of various combinations of 3 different bases, one of 

 which, when united to dephlogisticated air, forms water, another fixed air, and 

 the third phlogisticated air ; and that by means of vegetation each of these sub- 

 stances are decomposed, and yield their dephlogisticated air ; and that in burning 

 they again acquire dephlogisticated air, and are restored to their pristine form. 



It seems therefore from what has been said, as if the phenomena of nature 

 might be explained very well on this principle, without the help of phlogiston ; 

 and indeed, as adding dephlogisticated air to a body comes to the same thing as 

 depriving it of its phlogiston and adding water to it, and as there are perhaps no 

 bodies entirely destitute of water, and as I know no way by which phlogiston 

 can be transferred from one body to another, without leaving it uncertain whe- 

 ther water is not at the same time transferred, it will be very difficult to deter- 

 mine by experiment which of these opinions is the truest ; but as the commonly 

 received principle of phlogislon explains all phenomena, at least as well as Mr. 

 Lavoisier's, I have adhered to that. There is one circumstance also, which 

 though it may appear to many not to have much force, I own has some weight 

 with rr.v. , it is, that as plants seem to draw their nourishment almost entirely 

 from water and fixed and phlogisticated air, and are restored back to those sub- 

 stances by burning, it seems reasonable to conclude that, notwithstanding their 

 infinite variety, they consist almost entirely of various combinations of water 

 and fixed and phlogisticated air, united according to one of these opinions to 

 phlogiston, and deprived according to the other of dephlogisticated air ; so that, 

 according to the latter opinion, the substance of a plant is less compounded than 

 a mixture of those bodies into which it is resolved by burning ; and it is more 

 reasonable to look for great variety in the more compound than in the more 

 simple substance. 



Another thing which Mr. Lavoisier endeavours to prove is, that dephlogisti- 

 cated air is the acidifying principle. From what has been explained it appears, 

 that this is no more than saying, that acids lose their acidity by uniting to phlo- 

 giston, which, with regard to the nitrous, vitriolic, phosphoric, and arsenical 

 acids, is certainly true. The same thing, I believe, maybe said of -the acid of 

 sugar ; and Mr. Lavoisier's experiment is a strong confirmation of Bergman's 

 opinion, that none of the spirit of nitre enters into the composition of the acid, 

 but that it only serves to deprive the sugar of part of its phlogiston. But as to 

 the marine acid and acid of tartar, it does not appear that they are capable of 

 losing their acidity by any union with phlogiston. It is to be remarked also, that 

 the acids of sugar and tartar, and in all probability almost all the vegetable and 



