390 WATT. 



said, that in no other person was there ever observed 

 so " fine an expression of reposing strength and unin- 

 terrupted self-possession as marked his whole manner." 



APPENDIX. 



HISTORICAL NOTE ON THE DISCOVERY OF THE THEORY OF 

 THE COMPOSITION OF WATER. 



THERE can be no doubt whatever, that the experiment of Mr. 

 Warltire, related in Dr. Priestley's fifth volume,* gave rise to 

 this inquiry, at least in England; Mr. Cavendish expressly 



* Mr. Warltire's letter is dated Birmingham, 18th April, 1781, 

 and was published by Dr. Priestley in the Appendix to the seventh 

 volume of his c Experiments and Observations relating to various 

 branches of Natural Philosophy ; with a continuation of the Ob- 

 servations on Air,' forming, in fact, the fifth volume of his l Ex- 

 periments and Observations on different kinds of Air ;' printed at 

 Birmingham in 1781. 



Mr. Warltire's first experiments were made in a copper ball or 

 flask, which held three wine pints, the weight 14 ounces ; and his ob- 

 ject was to determine " whether heat is heavy or not." After stating 

 his mode of mixing the airs, and of adjusting the balance, he says, 

 he "always accurately balanced the flask of common air, then found 

 the difference of weight after the inflammable air was introduced, 

 that he might be certain he had confined the proper proportion of 

 each. The electric spark having passed through them, the flask 

 became hot, and was cooled by exposing it to the common air of the 

 room 1 it was then hung up again to the balance, and a loss of weight 

 was always found, but not constantly the same ; upon an average it 

 was two grains." 



He goes on to say, u I have fired air in glass vessels since I saw 

 you (Dr. Priestley) venture to do it, and I have observed, as you 

 did, that, though the glass was clean and dry before, yet, after firing 

 the air, it became dewy, and was lined with a sooty substance." 



It 



