Miscellaneous. 359 
~spects does it differ from the wave motion of light and 
heat? It is evident that the existence of two opposite 
electrical states must involve some kind of polarity or direc- 
tionality in the motion, not required to explain the pheno 
mena of light and heat. The probable dependence of 
-magnatism on the circulation of the magnet would seem to 
suggest the idea of circular waves; if these be supposed 
analogous to the waves of eircularly polarized light, the 
phenomena of electric polarity may be readily explained. 
Moreover, the state of mutual inductive constraint of the 
electricity of two opposed, @nd oppositely electrified sur- 
faces may be roughly symbolized by the condition of 
spiral springs, mutually compressing each other againihe an 
intervening obstacle. 
In the hope that these remarks may induce some of 
your readers to direct their thoughts to the elucidation of 
an important point of physics, 
I remain, &c., 
CHARLES BROOKE. 
Fitzroy Square, W. 
MISCELLANEOUS. 
POWER OF COAL.—The best anthracite coal has been 
found to contain 98 per cent. of carbon. Favre and Sil- 
berman found that if all the heat is utilised, one pound of 
carbon in burning will generate sufficient heat to raise the 
temperature of 8,080 pounds of water one degree of the 
centigrade scale; and, according to Andrews, it will heat 
7,900 pounds one degree. Taking the smaller of these re- 
sults, 7,900 pounds, and reducing it, we find that one pound 
of carbon will raise the temperature of 14,220 pounds of 
water one degree of Fahrenheit’s scale. Multiplying this 
by Joule’s equivalent, 772, and we have 10,977,840 foot- 
pounds as the quantity of work which one pound of carbon 
will perform. If wesuppose it burned at the rate of one 
pound per hour, by dividing the foot-pounds of work by 
33,000 and by 60, wdshall have the horse-power 54. If all 
its heat could be utilized, therefore, we should have a horse- 
power from two-elevenths of a pound of coal per hour. 
mew SERIES:—VOL, «1. Gre 
