500 PHILOSOPHICAL TRANSACTIONS. [ANNO 1784. 



shown that plants growing in the dark, in water alone, will increase in size, 

 without yielding dephlogisticated air, and without the water hecoming more 

 impregnated with it than before, no objection can be drawn from thence. Mr. 

 Senebier finds, that plants yield much more dephlogisticated air in distilled water 

 impregnated with fixed air, than in plain distilled water, which is perfectly con- 

 formable to the above-mentioned hypothesis ; for as fixed air is a principal con- 

 stituent part of vegetable substances, it is reasonable to suppose that the work 

 of vegetation will go on better in water containing this substance, than in other 

 water. 



There are several memoirs of Mr. Lavoisier published by the Academy of 

 Sciences, in which he entirely discards phlogiston, and explains those pheno- 

 mena which have been usually attributed to the loss or attraction of that sub- 

 stance, by the absorption or expulsion of dephlogisticated air ; and as not only 

 the foregoing experiments, but most other phenomena of nature, seem expli- 

 cable as well, or nearly as well, on this as on the commonly believed principle 

 of phlogiston, it may be proper briefly to mention in what manner I would ex- 

 plain them on this principle, and why I have adhered to the other. In doing 

 this, I shall not conform strictly to his theory, but Bhall make such additions and 

 alterations as seem to suit it best to the phenomena ; the more so, as the fore- 

 going experiments may perhaps induce the author himself to think some such 

 additions proper. 



According to this hypothesis, we must suppose that water consists of inflam- 

 mable air united to dephlogisticated air ; that nitrous air, vitriolic acid air, and 

 the phosphoric acid, are also combinations of phlogisticated air, sulphur, and 

 phosphorus, with dephlogisticated air ; and that the two former, by a further 

 addition of the same substance, are reduced to the common nitrous and vitriolic 

 acids ; that the metallic calces consist of the metals themselves united to the 

 same substance, commonly however with a mixture of fixed air ; that on expos- 

 ing the calces of the perfect metals to a sufficient heat, all the dephlogisticated 

 air is driven oft", and the calces are restored to their metallic form ; but as the 

 calces of the imperfect metals are vitrified by heat, instead of recovering the 

 metallic form, it should seem as if all the dephlogisticated air could not be driven 

 off from them by heat alone. In like manner, according to this hypothesis, the 

 rationale of the production of dephlogisticated air from red precipitate is, that 

 during the solution of the quicksilver in the acid and the subsequent calcination, 

 the acid is decompounded, and quits part of its dephlogisticated air to the quick- 

 silver, whence it comes over in the form of nitrous air, and leaves the quicksilver 

 behind united to dephlogisticated air, which, by a further increase of iieat, is 

 driven off, while the quicksilver re-assumes its metallic form. In procuring de- 

 phlogisticared air from nitre, the acid is also decompounded ; but with this dif- 



