APPENDIX. 111 
recombination of the elements. Thus it appears 
that electricity is a grand agent for converting 
‘ heat and the ordinary forms of mechanical power 
into one another. 
I have lately been at considerable pains in 
framing a theory of heat more natural and more 
consistent with facts than the undulatory hypo- 
thesis. Setting out with the discovery of Fara- 
day, that every atom is associated with the same 
absolute quantity of electricity, I assume that 
these atmospheres of electricity revolve with 
enormous rapidity round their respective atoms ; 
that the momentum of the atmospheres consti- 
stutes ‘‘caloric,” while the velocity of their ex- 
terior circumferences determines what we call 
temperature. The theory applies very beautifully 
to the phenomena of conduction, and satisfies 
rigorously the law of Boyle and Mariotte with 
respect to elastic fluids. When applied to the 
doctrine of sp. heat, it demands the extension 
of the law of Dulong and Petit to all bodies, 
whether compounds or not, and points out the 
following general law, applicable to all bodies 
except perhaps compound gases, viz., the specific 
heat of any body is proportional to the number of 
atoms in combination divided by the atomic weight, 
