1833.] Attraction and Repulsion. 443 
that is, how far the attraction between atoms (chemical and cohe- 
sive) is increased towards any given atom by the mass. 
4thly. In what ratio of the distance the force of attraction of atoms 
varies; which will lead me to confirm by arguments the opinion that 
gravitation and contiguous attraction are the same property of mat- 
ter, differing only in the circumstances under which it is presented to 
our observation. 
Ist. Of the distance at which attraction of atoms operates. 
From the effects of cohesive attraction being in most cases evident 
only at very small distances, and from the particles of bodies in the 
aerial state actually appearing to repel each other, it has been gene- 
rally inferred that this force is exerted only at very limited distances ; 
and hence its name, contiguous attraction. 
Although the effects of cohesive attraction may be apparent only 
at very small distances, yet it is scarcely correct to infer that this force 
is exerted only at such distances until due attention has been paid to 
the causes, which, by affecting the phenomena, may create deception 
upon the mind. These appear to me of two kinds,—the minuteness 
of attracting atoms, and all causes which operate against the attrac- 
tion of atoms. 
On the magnitude of atoms must in a great measure depend the 
greatest distance at which the force of their attraction is sufficiently 
powerful to be apparent. 
If it be admitted that the force of this attraction decreases in as 
great a ratio of the distance as that of gravitation, then, since atoms are 
so small as not to be perceptible to our senses, it will follow that how- 
ever strong their attraction may be when almost contiguous to each 
other, it will not be apparent at any mensurable distance, though in 
fact, it may be exerted in some degree at unlimited distances ; for if 
two attracting particles of matter were sufficiently increased in magni- 
tude without altering at all the laws of their attraction, this force 
might be evident at any distance however great, unless it be supposed 
(which would indeed be very unphilosophical) that attraction ceases at 
some certain distance suddenly and abruptly. 
The other causes which may create deception as to the distance at 
which this attraction is exerted, are all powers which oppose its force. 
From the attraction of particles being constantly opposed by the 
powerful agency of heat, its force in liquids is scarcely apparent, though 
in fact it may be very powerful, for it is only the excess of the attrac- 
tion over the repulsion that can be measured. 
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