Alas, Gentlemen, for human predictions and posthumous fame I 

 Who could have foreseen that, ere thirty years had elapsed, so opposite 

 a view of the labours and character of this philosopher would pro- 

 ceed from one of the most enlightened of his successors ? But for the 

 sake of justice, and because there is no page in the histoiy of expe- 

 rimental philosophy more instructive than that to which this question 

 carries us back, I now ask permission to give equal publicity to a 

 different view, and to offer such a sketch of the great chemical dis- 

 covery of the composition of water, as may perhaps help to eluci- 

 date the truth. 



According to the statements of this publication, the person who 

 brought the first evidence of the composition of water, by proving that 

 the water produced is equal in weight to the gases consumed in its pro- 

 duction, was Dr. Priestley ; the person who first drew the conclusion 

 that water is composed of oxygen and hydrogen, was Watt. Now, the 

 former of these statements has not only no real foundation, but is con- 

 tradicted by the repeated assertions of Priestley himself, who constantly 

 maintained, that in no experiment made with care had he ever found 

 the weight of the fluid produced, equal to the sum of gases, or the fluid 

 itself pure water. The latter. Gentlemen, has no foundation, except in 

 the licence which M. Arago has used, of quoting the words of Watt 

 otherwise than they really stand. Nor can there be a stronger instance 

 of the inconvenience of such translations, than the difference of mean- 

 ing and value in the words thus substituted for each other— hydrogen^ 

 for example, put iov phlogiston. 



What is it, Gentlemen, that gives importance to this discovei'y in the 

 history of science ? Not merely, as has been too popularly stated, that 

 it banished water from among the elements, but that whilst it accounted 

 for an infinite number of phaenomena, it introduced into chemistry 

 distinctness of thought and accuracy of reasoning, and led to the gene- 

 ral prevalence of a sounder logic. The prejudice of that epoch was, 

 not to regard compound substances as simple, but to consider un- 

 decompounded substances as compound. The hypothesis, that a prin- 

 ciple called Phlogiston entered into the composition of a great variety 

 of bodies which we now consider simple, had infected the whole of che- 

 mistry. This hypothesis, at first but a conjectural attempt to generalise 

 the phsenomena of combustion, gradually made itself a coat of patch- 

 work out of the successive discoveries of half a century, and arrived 

 at playing as many feats in philosophy, as the harlequin in a pantomime. 

 In the very paper of Watt on which this claim is founded, we find, 

 first, inflammable gas, then charcoal, then sulphur, then nitrogen, to be 



