THE CONSTITUTION OF MATTER. 
475 
to figure tliesc atoms not as weighing fractions of ordinary units of weight; 
may we not say that they hold the place of the “ centres’’ of force just referred 
to, that they are, in fact, infinitely small P 
Supposing such a modification admitted, the usual atomic theory becomes 
nearly identical with the theory of Boscovich. Atoms, on this view, occupy 
a position with regard to masses analogous to that of mathematical points, by 
the juxtaposition of which lines, surfaces, and solids are generated. A line, 
it is obvious, may be divided by a ruler or other mechanical means into any 
number of shorter lines, but these are still made up of many points. The 
analysis of a line into its constituent points can only be effected mentally ; it 
is, however, not a very easy thing even to imagine a point, because it cannot 
truly be compared to anything we have ever seen. So with atoms, the 
matter of bodies. Neither the points nor the atoms have any real, tangible 
existence as bodies, but we are not on that account precluded from reasoning 
upon them as though they had. Moreover, we do not always construct 
theories because we believe them to represent faithfully what is actually the 
case, to stand in the position of absolute truths, but because they enable us 
to co-ordinate phenomena, and bring within reach many things which would 
otherwise lie out of the sphere of our limited intellectual capacity. This 
hypothesis requires the absolute weights of the atoms to be reduced propor¬ 
tionately to tlicir magnitude; they must be assumed infinitely small; neverthe¬ 
less, t hough infinite, they may bear to each other the ratios which we commonly 
express as atomic weights. It may seem an anomaly that masses should be 
acted upon by gravity—that is, have weight—whilst their constituent parts 
have not; but the anomaly vanishes if we allow that infinite smallness is not 
absolutely nothing. 
Such a view of the constitution of matter seems to me to be more in har- 
mony with the general plan of nature, so far as science has at present been 
enabled to tra^e it, than any based upon the exclusion of the idea of infinite 
divisibility. It allows us to form at least rough conjectures as to the mode 
of action and reaction subsisting, not only between the different forces them- 
selves which are known to affect matter, but also between these forces and 
matter itself as the subject of their operations. No corpuscular hypothesis, 
as we may distinguish Dalton’s atomic theory, does, nor can, elucidate, how¬ 
ever crudel} 7 , the modus oyer an di of such as are denominated imponderable 
agents, in their relations to ordinary ponderable matter. I can see no way 
of explaining in a rational manner processes of photography or the action of 
heat in promoting chemical combinations, upon the assumption of finites as 
the objects and infinites as the agents in the operation. But if we superadd 
to the ordinary hypothesis the conception of infinity extended to the 
weight as well as magnitude of atoms, we reduce to a minimum the difficulty 
of correlating our ideas of ordinary matter with those of the mysterious 
agencies, light, heat, and the other “ physical forces.” 
Of recent years our notions of the nature of the phenomena which we as¬ 
cribe to these invisible agents have gradually suffered complete revolution. 
It is less than a century ago when the opinion was very generally held among 
men of science, that the phenomena of heat were due to the existence of a 
peculiar substance or form of matter called “caloric.’’ According to this view, 
bodies became heated by absorbing caloric ; they became cold by losing 
caloric; radiation of heat was the shooting out of particles of caloric; the 
phenomena of specific and latent heat, in like manner, were thought to be oc¬ 
casioned by a varying tendency to a kind of combination between the parti¬ 
cles of ordinary matter and those of this subtle material, caloric. 
In this our time, all these changes are universally believed to be caused by 
motion. Vibratory motion of the particles of bodies is supposed always to 
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