488 Rev. W. V. Harcourt on Lord Brougham's statements 



this dissolution is fire, adding that this was done by a nitrous 

 substance inherent in, and mixed with, the air." 



Here was the first distinct conception, and evidence, of the 

 composition of the atmosphere. The French physician Rey 

 had before proved that air enters into fixed combination with 

 solid matter: his proof rested on a capital observation which 

 he quotes from the Basilica Antimonii of Hamerus Poppius : 

 thischemist, " placing," says Rey, " a burning glass in the sun's 

 rays, directed their focus on the apex of a cone of antimony, 

 till the whole becomes white, when the calcination is complete. 

 It is a wonderful thing, Poppius added, that although in this 

 calcination the antimony loses much of its substance by the 

 vapours and fumes which exhale copiously, yet so it is, its 

 weight increases instead of diminishing*." The philosophical 

 acumen of Rey seized on the truth unequivocally shown in 

 this simplified form of calcination, in which he discerned the 

 presence of but two ponderables, and he concluded, — 1. That 

 the increase of weight arose from the air being solidified in 

 the antimony ; 2. That the two substances combined to a de- 

 finite degree of saturation ; 3. That the increase of weight ob- 

 served in other metals, whether by calcination or simple expo- 

 sure to the air, is due to the same cause — conclusions which, 

 if their publicity had been equal to their value, would doubt- 

 less have been recorded for the early and distinct enunciation 

 which they contain both of a fundamental principle, and an 

 important though as yet unanalysed fact, as the first step in 

 this branch of science, in consequence as well as timef. 



But Rey, though he recognised the ponderable and combi- 

 ning qualities of air, considered it with the other philosophers 

 of his day, as an element simple in essence, though mutable 

 in form : and the first scientific question of the accuracy of 

 this supposition was raised by Boyle in 1654. In the same 

 Essay in which his discovery of the factitious airs was an- 

 nounced, he quoted from Paracelsus the following remarkable 

 passage : — " As the stomach converts meat, and makes part of 

 it useful to the body, rejecting the other part, so the lungs con- 



* Essay 25. 



•j* Rey's work was first published in 1630. It contains, besides the spe- 

 culation here mentioned, a just correction of the view which the schools had 

 taken of a fact affirmed in the Physics of Aristotle — that a blown bladder 

 is heavier than an empty one. Rey showed that this is true only if the 

 bladder be blown to such a degree as to compress the air, and that the fact, 

 so stated, is a real proof that the air has absolute weight. This is perhaps 

 the first correct published statement of the weight of air, as an experimental 

 fact. It is evident however from a letter of Baliani, quoted by Venturi, 

 that Galileo had not only taught the same doctrine, but made his experi- 

 ments on the specific gravity of the air before 1630. 



