LIFE of Dr HUTTOK 79 



plain the phenomena of light, heat, and electricity. He confider- 

 ed all thefe three as modifications of the folar fubftance, and 

 thought that many of the appearances they exhibit, are only to 

 be explained, on the fuppofition that they confift of an expan- 

 five force, of which inertnefs is not predicable ; in particular, 

 that light is a power propagated from the fun in all directions, 

 like gravity, with this difference, that it is repulfive, while gra- 

 vity is attractive, and requires time for its tranfmifhon, which 

 the latter does not, at leaft in any fenfible quantity *. 



The profecutionof this fubject has led him to confiderthe nature 

 of phlogiston, a fubftance once fo famous in chemiftry, but of 

 which the name has almoft as entirely difappeared from the vo- 

 cabulary of that fcience, as the word Vortex from the language 

 of phyfical aftronomy. The new and important experiments 

 made on the calcination of metals, and on the compofition of 

 water, are, as is well known, the foundations of the antiphlogi- 

 flic theory. Nobody was more pleafed than Dr Hutton with 

 thefe experiments, nor held in higher eflimation the character 

 and abilities of the chemifls and philofophers by whom they 

 were conducted. He was neverthelefs of opinion, that the con- 

 elufions drawn from them are not altogether unexceptionable, 

 nor deduced with a fufficient attention to every circumftance. 

 This remark he thought peculiarly applicable to what regards 

 the compofition of water, to the phenomena of which experi- 

 ment, the differtation we are now fpeaking of is chiefly directed. 

 The two aeriform fluids, it is there obferved, which compofe 

 water, in order to unite, muft not fimply be brought together, 

 for in that ftate they might remain for ever unchanged, but they 

 muft be fet on fire, and made to burn, and from this burning 

 there are evidently two fubftances which make their efcape 3 

 Vol. V. — P. III. L namely, 



* See Differtations V. and VI. on Matter and Motion, in the work above quot- 

 ed. The Chemical Differtation on Phlogifton is in the fame volume, p. 171, 



