of Heat, Gases, and Gravitation. 131 
new doctrines till their principles shall be shown to be without 
objection; therefore, I beg of Mr. Herapath to consider with at= 
tention the following remarks, and to consider their sole object 
to be the advancement of knowledge. 
We are utter strangers, but we meet on the same area in the 
most honourable species of contest that human powers can be en- 
gaged in; let it, therefore, be conducted with fairness and ho- 
nour. : é 
The first point to which I would direct Mr. Herapath’s atten- 
tion is; that the mere solution of certain phenomena, or ascer- 
taining the ratio of certain forces, is not a sufficient reason for 
adopting a new hypothesis, unless the assumed principles be 
consistent with universal experience. 
If the assumed principles, or any one of them, be not true, 
every conclusion derived from those principles must fall to the 
ground. os 
If any one of the assumed principles cannot be directly esta- 
blished by a reference to unquestionable experience, the conclu- 
sions must remain hypothetical, notwithstanding that an expla- 
nation of some phenomena may be effected by such hypotheses. 
On these grounds, which | think are unobjectionable, 1 must 
reject Mr, Herapath’s 4th postulatum, wherein he assumes that 
“¢ heat arises from an intestine motion of atoms, or particles.” 
We have no direct evidence of the existence of such intestine mo- 
tion, nor of an analogous motion producing like effects. The 
assumption of such a principle resembles contriving an empirical , 
formula which within certain limits approximates to the truth, 
but no general conclusion ean be established by it, and every par- 
ticular one must be proved by experience before it can be relied 
upon, : 
Besides, the vibratory motion of the parts of bodies kas not 
been shown to be a consequence of proximity to a hot body by 
any established mechanical principle. Of the truth of this asser- 
tion I hope he will be satisfied when some of his propositions 
have been examined. 
Mr. Herapath assumes that matter is inert in his first postu- 
Jatum ; we have not, in my opinion, any grounds for this assump- 
tion; matter is never found inert in nature, unless the forces acting 
upon it be exactly balanced. 
The repulsive force of the particles of gases, is one of these 
principles which has been assumed without strict examination ; 
the elastic force of a gas seems to be better explained by its at- 
traction for heat, than by the anomalous doctrine of variation. 
from attraction to repulsion. If we consider heat to be a ma- ' 
terial fluid, this and many other phenomena are easily explained. 
R 2 I only 
