Lord Brougham on the Composition of Water. 317 



but Mr Cavendish himself, p. 127, expressly states Mr Warltire to have 

 observed it, and cites Dr Priestley's 6th volume. 



Mr Cavendish himself could find no loss of weight, and he says that 

 Dr Priestley had also tried the experiment, and found none/' But Mr 

 Cavendish found there was always a dewy deposit, without any sooty 

 matter. The result of many trials was, that common air and inflammable 

 air being burnt together, in the proportion of 1000 measures of the former 

 to 423 of the latter, " about one-fifth of the common air, and nearly all 

 the inflammable air, lose their elasticity, and are condensed into the dew 

 which lines the glass." He examined the dew, and found it to be pure 

 water. He therefore concludes, that " almost all the inflammable air, 

 and about one-sixth of the common air, are turned into pure water." 



Mr Cavendish then burned in the same way dephlogisticated and in- 

 flammable airs (oxygen and hydrogen gases), and the deposit was al- 

 ways more or less acidulous, accordingly as the air burnt with the in- 

 flammable air was more or less phlogisticated. The acid was found to 

 be nitrous. Mr Cavendish states, that " almost the whole of the inflam- 

 mable and dephlogisticated air is converted into pure water." And, again, 

 that " if these airs could be obtained perfectly pure, the whole would be 

 condensed." And he accounts for common air and inflammable air when 

 burnt together not producing acid, by supposing that the heat produced 

 is not sufficient. He then says that these experiments, with the excep- 

 tion of what relates to the acid, were made in the summer of 1781, and 

 mentioned to Dr Priestley, and adds, that "a friend of his (Mr Caven- 

 dish's) last summer (that is 1783) gave some account of them to Mr La- 

 voisier, as well as of the conclusion drawn from them, that dephlogisti- 

 cated air is only water deprived of its phlogiston ; but at that time so 

 far was Mr Lavoisier from thinking any such opinion warranted, that till 

 he was prevailed upon to repeat the experiment himself, he found some 

 difficulty in believing that nearly the whole of the two airs could be con- 

 verted into water." The friend is known to have been Dr, afterwards 

 Sir Charles Blagden ; and it is a remarkable circumstance, that this pas- 

 sage of Mr Cavendish's paper appears not to have been in it when ori- 

 ginally presented to the Royal Society, for the paper is apparentlj' in Mr 

 Cavendish's hand, and the paragraph p. 134, 135, is not found in it, but 

 is added to it, and directed to be inserted in that place. It is moreover 

 not in Mr Cavendish's hand, but in Sir Charles Blagden's, and indeed the 

 latter must have given him the information as to Mr Lavoisier, with whom 

 it is not said that Mr Cavendish had any correspondence. The paper 

 itself was read 15th January 1784. The volume was published about six 

 months afterwards. 



Mr Lavoisier's memoir (in the Mem. of the Academic des Sciences for 

 1784) had been read partly in November and December 1783, and addi- 



• Mr Cavendish's note, p. 127, would seem to imply this ; but I have not 

 found in any of Dr Priestley's papers that he has said so.— Note bv Mr Jambs 

 Watt . 



vol.. XXVII. NO. HV.— "OCTOBER 1839. Y 



