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



reserved for Dalton, whose first views of that important in- 

 duction were suggested perhaps by these very conjectures of 

 Newton ? 



In other respects the theory of affinities is hardly laid down 

 by him with more distinctness in this mature work, than in 

 his younger speculations, in the earliest of which he applied 

 it, as an universal property of bodies, to supposed aetherial 

 fluids, and in the next to the factitious airs then recently dis- 

 covered. 



The chemist who remembers the modern observation, that 

 gases (including that vital aerial spirit to which Newton com- 

 pared his aether) are powerfully condensed in the pores of 

 charcoal, on the surface of metals, and in the interior of a ball 

 of spongy platina, cannot fail to be struck with the singular 

 anticipation which the^rs^ of Newton's hypotheses display, of 

 a close connexion between molecular attractions and chemical 

 changes, and a subjection of the most elastic of bodies to both 

 these forces in common. Nor will his admiration be dimi- 

 nished, when he finds the theory of elective and mediating 

 affinities first broached for such a purpose as to explain the 

 dark phaenomena of muscular motion, and the material means 

 through which the soul acts on the body, by the supposition 

 of relative degrees of sociableness and unsociableness between 

 the brain and muscles on the one hand, and on the other, a 

 conjectural array of aetherial fluids imagined to be even rarer 

 and more elastic than the most subtle and repulsive air *. 



After this, we are not astonished to find the same master 

 mind, in its second survey, so laying down the theoretical map 

 of gaseous chemistry, that in truth the chemists who followed, 

 down to the sera of Higgins, Dalton, and Gay-Lussac, did 

 little more than work out by experiment the principles which 

 Newton had assumed. 



The application of chemical principles to aetherial matter is 

 contained in a letter to Oldenburg, from which I have already 

 given some quotations, read before the Royal Society in Dec. 

 1675. This elaborate communication, strange to say, has 

 never been printed, except in the ponderous and seldom 

 opened volumes of Birch's history of that Society, and conse- 

 quently is scarcely known, even in our own country, to men 

 of science, otherwise than by a few extracts from that part of 

 it which relates to light, published in the Philosophical Trans- 

 actions by Dr. Young. 



The theory of gases, as communicated to Boyle in 1678, 

 you will find in Birch's life of that philosopher, or in New- 

 ton's collective works. In his letter to Boyle, after supposing 



* Letter to Oldenburg, Registry of the Royal Society, vol. v. 



