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oh 
FROM THE HIGHER ATMOSPHERE. 467 
in the paper now. submitted to the Society, it will be hence 
expedient to take a retrospect of the facts which have been 
disclosed relative to the communication of heat, In framing 
this abstract, I shall abstain from all hypotheses, which might 
assist, only to deceive, the imagination, but content myself with 
stating the facts really ascertained, and with tracing out be 
sarwelgpicgean to which they distinctly lead. 
I have observed, that Heat never appears in a detached 
form. Yet its materiality is evinced, by the expansion which 
it invariably communicates to the substances with which it 
unites. _ While it is attracted by any bodies, therefore, it must 
introduce into them some repulsive force, which had previously 
existed among its own particles.. Heat must hence be a fluid 
of extreme tenuity, yet endued with an_ irresistible elastic 
force. . But when a substance, either from a chemical or. me- 
chanical impression, suffers a sudden change of constitution, 
and makes a copious discharge of heat, this emission is al- 
ways accompanied by an effulgent light. On the other hand, 
when the rays of the sun, or even those of a bright lamp, 
are intercepted by any body, and seem lost or extinguished, 
a corresponding increase of warmth is immediately betrayed 
at the absorbing surface. It follows from this and similar 
facts, that heat is the same fluid as light, only in a state of rest 
and combination. In short, heat is latent, invisible, light,— 
the agelov gus of the ancients,—which has been arrested in its 
rapid flight, and cannot again be liberated, without such a 
. violent change of condition, as will leave entire the repulsion 
of its own particles, to create the requisite projectile force. 
In ordinary cases, however, the light remains imprisoned in 
the substance with which it combines, and only migrates from 
one portion to another. ; aie 
3N 2 The 
