385 
of Edinburgh^ Session 1864-65. 
merely a mental affection, called up by an impulse on the optic 
nerve made by the movements of the luminiferous ether, wliicb, not 
the chair or table, but the forces existing and acting external to 
the chair or table, or other object, radiates off. Moreover, it is 
universally admitted, that vision is only a mental affection, not cor- 
responding to anything external to the mind. 
Chemical atoms may therefore be regarded as circles of force 
without any nucleus or core of matter in them ; for if the forces 
are the efficient parts, there is evidently no necessity to assume 
that an inert and useless part will exist within them. The law of 
Parsimony entirely justifies us in assuming this, and in discharging 
matter from the atom. 
The universe in this light becomes a vast and glorious exhibition of 
Idowevj acting and displayed according to those laws which have been 
impressed, and which laws and system we designate the laivs of nature. 
Sir John Leslie, in his Dissertation prefixed to the Encyclo- 
paedia Britannica,” seems to have no disfavour to Boscowich’s 
“Theory of Dynamics,” except that the material points are made 
mathematical points, and suggests that, in order to get over this 
prejudice, we may conceive the material centres “ to have real 
dimensions, though far smaller than any assigned measure.^’ 
Professor Eorbes, in his Dissertation, expresses a difficulty in 
reconciling this theory to the law of inertia. This is probably a 
chief difficulty felt by most men, to conceive of inertia being pos- 
sessed by immaterial bodies. But the difficulty is entirely imagi- 
nary, and arises from our habit of considering that matter has 
inertia^ and conceiving that therefore nothing but matter can have 
it. It is evident we cannot declare what properties are incompa- 
tible with immaterial forces. Our proof that we must admit them 
to have inertia is this. Let us suppose a molecule of forces at rest ; 
it evidently will not move unless force is applied ; a certain amount of 
force is required to give it a certain velocity. If this be admitted, then 
it follows that if the molecule be increased 10, 100, or 1000 times 
in mass.! it must necessarily require 10, 100, or 1000 times that force 
to produce the like velocity. So far, then, as we have analogy and 
argument to guide us, these immaterial bodies must have inertia^ 
at least the mouth is shut against declaring that they cannot have it. 
If a difficulty still remains in conceiving immaterial masses to 
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VOL. V. 
