SUN FORCE AND EARTH FORCE. 
331 
particles, lie holds, it lias repulsion ; for the particles of all 
ponderable matter it has affinity ; it attracts the particles of 
ponderable matter with forces which vary inversely as the 
squares of the distance. It thus acts through ponderable 
matter. If universal space were filled with caloric, sun 
force, alone (without ponderable matter), caloric would also be 
inactive, and would constitute a boundless ocean of powerless or 
quiescent ether, because it would then have nothing on which 
to act; while ponderable matter, however inactive of itself, 
“ has certain properties by which it modifies and controls the 
actions of caloric, both of which are governed by immutable 
laws that have their origin in the mutual relations and specific 
properties of each.-” 
And he lays down a law which he believes is absolute, and 
which is thus expressed : — 
“By the attraction of caloric for ponderable matter it 
unites and holds together all things; by its self-repulsive 
agency it separates and expands all things.-” 
As I have already said, the tendency of modern teaching 
is to rest upon the hypothesis which Lord Bacon sustained, 
which Count Rumford sought to prove by experiment, and 
which through the days of Boyle and Newton, even down to the 
time of Sir Humphrey Bavy, has been received, viz., that heat is 
motion, or, as it would perhaps be better stated, a specific 
force or form of motion. 
But this hypothesis, popular as it is, is not one that ought to 
be accepted to the exclusion of the simpler view of the 
material nature of sun force and of its influence in modifying 
the condition of matter. We do not yet know sufficient to be 
dogmatic, and the very terms we now use to express differences 
of opinion and thought may in the ages to come be traced out 
as referring after all to some single principle or agency which, 
not being clearly definable now, admits of being seen from 
different sides and of seeming what it really is not. We are 
bound therefore to study every thought that is presented to us 
honestly and fully, and to consider it by its own reason and on 
its own merits ; not to measure it by some other hypothesis as 
the standard, or representation, or type. By this method of 
examination, then, the hypothesis of Metcalfe respecting sun 
force and earth force is not only very simple, but most 
fascinating. It is so easy that a child may read it, and thus it 
reads. 
Here are two elements in this universe : the one is pon- 
derable matter; it can be seen, touched, weighed, and it is 
made up of particles infinitely minute, so miuute that according 
to I)r. Thompson the ultimate particle of lead, which is 
assumed to be large, cannot be estimated at more than the 
vol. v. — no. xx. 2 a 
