206 
was indicated by the late Mr Robert Brown, the botanist, and his 
literary executor, Mr J. J. Bennett of the British Museum, has 
brought them before the Royal Society of London. They are both, 
contrary to general expectation, published statements contained in 
well-known works. The first is a section of De Luc’s “ Xdees sur 
la Meteorologie,” entitled, 44 Anecdotes relatives & la decouverte de 
i’Eau sous la forme d’Air,” in which the following decisive decla- 
ration occurs : — 
44 Yers la fin de Y annee 1782, J’allai a Birmingham ou le 
Dr Priestley s’etoit etabli depuis quelques annees. XI me eom- 
muniqua alors, que M. Cavendish, d’apres une remarque de M. 
Warltire; qui avoit toujours trouve de Veau dans les vases on il 
avoit brule un melange d’air inflammable et d’air atmospherique ; 
s’etoit applique a decouvrir la source de cette eau, et qu’il avoit 
trouve, 4 qu’un melange d?air inflammable et df air dephlogistiquS 
en proportion convenable, etant allume par l’etincelle electrique, se 
convertissoit tout entier en eau, 9 Je fus frappe, en plus haut degre, 
de cette decouverte/’ ( Idees , &c., tome ii., 1787, pp. 206-7.) 
The important testimony thus borne to Cavendish’s experiment 
having had as its object the discovery of the source of the water 
which appeared when hydrogen and oxygen are burned together ; 
as its phenomenal result that in certain proportions a given weight 
of the gases in question could be burned into the same zueight 
of water ; and as its logical induction that the gases had been con- 
verted into the water , constituted Cavendish a discoverer of the com- 
position of water. And as this conclusion was drawn in 1782, 
whilst Watt, the earliest counter-claimant of the discovery, did not 
draw his similar conclusion till 1783, the priority unquestionably 
belonged to Cavendish, who was thus the discoverer of the composite- 
ness of water. 
Reference was then made to the effort of Mr Muirhead to under- 
value De Luc’s testimony, on the plea that in another part of the 
44 Xdees” its author declared himself to have been ignorant of Ca- 
vendish’s conclusions till 1783, and not to have learned them till 
after he was familiar with those of Watt. It was contended, on the 
other hand, that De Luc’s two statements were not contradictory, 
but perfectly reconcileable with each other, — the one referring to Ca- 
vendish’s interpretation of his experiments on firing hydrogen and 
oxygen, which De Luc learned from Priestley in 1782 ; the other to 
