298 On the Affinities of Bodies for Light, 
that their request has been complied with, and we may ex- 
pect some excellent results from their labours. 
In the mean time they invite chemists to continue their 
scrupulous researches into the composition of bodies. «* On 
our part,” they add, ‘* we shall neglect nothing in order 
to multiply our observations upon solid bodies, liquids, 
and aériform fluids; and perhaps we may still owe some 
useful result to the happy analogy unfolded to us by Newton. 
These researches seem already sufficiently advanced to pre- 
sent a method of verifying to a certain point the chemical 
analyses of transparent bodies; and it is, perhaps, a result 
~ singular enough in itself that we may penetrate so far tnto 
the composition of bodies, and ascertain, in a sufficiently con- 
nected manner, the nature and proportions of their princi- 
ples by the geometrical instrument called a repeating circle.” 
The authors remark that the results they have obtained 
are yery favourable to the system of the emission of light, 
and appear to be contrary to that of the undulations of 
light. ‘In fact,” they say, ‘in the first system one should 
conceive that the refracting powers of compounds ought to 
depend on those of their principles. The combination of 
the attractive powers should take place proportionally to the 
masses ; and the little influence of condensation only proves 
the prodigious relative distance of the particles of light, as 
well as their extreme tenuity relative to the molecules of 
bodies and to the distances which separate them; circum- 
stances which are already indicated by many other pheno- 
mena. But if we supposed with Huyghens and the partisans 
of his doctrine, that light is produced by the vibrations of a 
very elastic substance, without transmission of substance, 
we could no longer conceive this relation so simple of com- 
pounds with their component parts; the condensation or 
the dilatation of the mediums ought necessarily to have a 
very complicated influence upon the progress, the direction, 
and the velocity of the numerous waves which are propa- 
gated: and what would not this influence be in the passage 
from the gaseous to the liquid state, when the constituent 
principles are collected under a volume two or three thou- 
sand 
