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 areat 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.