LORD BROUGHAM S APPENDIX. 477 



deprived of their latent heat, from the union of the bases 

 of inflammable air and of dephlogisticated air ; if this idea 

 had been accompanied in their minds by as much clearness 

 as in that of Lavoisier, they would certainly have avoided the 

 uncertainty and obscurity which I have pointed out.* 



As far as relates to Watt, the following are the new facts 

 that we have succeeded in establishing. 



1. There is no proof that anybody had given, in a written 

 document, anterior to Watt, the present theory of the compo 

 sition of water. 



2. Watt established this theory during the year 1 783, in 



* At the foot of p. 333, of the Transactions (for 1784), in a part of 

 his April letter, 1783, printed in italics, Watt said : &quot; Are we not 

 then authorized to conclude that water is composed of dephlogisti 

 cated air and phlogiston deprived of part of their latent or elemen 

 tary heat; that dephlogisticated air, or pure air, is composed of water 

 deprived of its phlogiston and united to elementary heat and light ; 

 that heat and light are contained in it in a latent state, since they do 

 not affect either the thermometer or the eye V If light is only a modi 

 fication of heat, or a peculiarity in its existence, or a constituent part 

 of inflammable air, then pure or dephlogisticated air is composed of 

 water deprived of its phlogiston, and united to some elementary 

 heat.&quot; 



Is not this passage as clear, precise, and intelligible as Lavoisier s 

 conclusions? (Note by Mr. Watt, jun.) 



The obscurity complained of by Lord Brougham in the theoretical 

 conceptions of Watt and of Cavendish appears to me unfounded. In 

 1784 they knew how to prepare two permanent and very dissimilar 

 gases. Those two gases were by some distinguished as pure air and 

 inflammable air; by others as dephlogisticated air and phlogiston ; 

 by others, finally, as oxygen and hydrogen. By the combination of 

 dephlogisticated air and phlogiston, they generated water weighing 

 as much as the two gases. Thenceforward water was no longer a 

 simple body; it was composed of dephlogisticated air and phlogiston. 

 The chemist who deduced this conclusion might have false ideas on 

 the internal nature of phlogiston without its casting any uncertainty 

 on the merit of his first discovery. Has it been even now mathemati 

 cally demonstrated that hydrogen (or phlogiston) is an elementary 

 body ; that it is not, as Watt and Cavendish for a time supposed, the 

 combination of a radical with a little water V (Note by M. Arago.) 



