512 
Proceedings of the Boyal Society 
ments on flexural vibrations of metal springs, which therefore 
prove imperfectness in the elasticity of flexure, such as he had 
previously proved for the elasticity of torsion.* 
2. The “ Doctrine of Uniformity” in Geology briefly 
refuted. By Professor William Thomson. 
The ‘‘ Doctrine of Uniformity ” in Geology, as held by many of 
the most eminent of British Geologists, assumes that the earth’s 
surface and upper crust have been nearly as they are at present 
in temperature, and other physical qualities, during millions of 
millions of years. But the heat which we know, by observation, 
to be now conducted out of the earth yearly is so great, that if this 
action had been going on with any approach to uniformity for 
20,000 million years, the amount of heat lost out of the earth 
would have been about as much as would heat, by 100° Cent., a 
quantity of ordinary surface rock of 100 times the earth’s bulk. 
(See calculation appended.) This would be more than enough to 
melt a mass of surface rock equal in bulk to the whole earth. 
No hypothesis as to chemical action, internal fluidity, effects of 
pressure at great depth, or possible character of substances in the 
interior of the earth, possessing the smallest vestige of probability, 
can justify the supposition that the earth’s upper crust has re- 
mained nearly as it is, while from the whole, or from any part, of 
the earth, so great a quantity of heat has been lost. 
Appendix. 
Estimate of present annual loss of heat from the earth. 
Let A be the area of the earth’s surface, D the increase of depth 
in any locality for which the temperature increases by 1° Cent., 
and h the conductivity per annum of the strata in the same locality. 
The heat conducted out per annum per square foot of surface in 
that locality is Hence, if we give h and D proper average 
* Proceedings of the Royal Society of London, May 1865. — W Thomson, 
“ On the Elasticity and Viscosity of MetalsT 
