Rensselaer Union, Volume 9, Number 26, Rensselaer, Jasper County, 15 March 1877 — The Age of the Earth as Determined by the Law of the Radiation of Heat. [ARTICLE]

The Age of the Earth as Determined by the Law of the Radiation of Heat.

The law bf the radiation of heat, as illustrated by some experiments with an ignited strip of platinum, has been applied in recent discussions respecting the age of the earth. Geological evidence has satisfactorily established that the temKure of the earth was formerly much sr than now, and the decline that has happened could only have taken place by radiation in space. Considering how slow the cooling now is—a scarcely perceptible fraction of a degree in the course of many centuries—it would seem that to accomplish the whole descent, if even we go no further back than the palezoic l era, an amazing lapse of time would be required. And if we accept the nebular hypothesis, since the original temperature must have lieen at least that of the temperature of the suq, the time must be correspondingly extended. Even if numbers could be given, the imagination would altogether fail to appreciate them. But we have here experimental proof that the higher the temperature of a body, the more rapidly it cools. A descent through a given number of degrees la more quickly made when a body is at a high than when it is at .low temperature. Anciently the cooling of the earth was more rapid than it is now. Not that there was any change or breach in the general law under which the operation was taking place, for the same mathematical expression applies to all temperature, no matter how high or low they may be. Mr. Croll, in his recent researches on the distribution of heat on the globe, points out the bearing of these experiments. Our estimate of the age of the earth, as deduced from the cooling she has undergone, must, therefore, in view of these considerations, be diminished—a result insisted upon by many recent authors. Too much weight must, however, not be given to this conclusion, since it ought to be borne in mind that the cooling was not taking place by radiation into space from the earth alone as a solitary body. She was in presence of a high extraneous temperature, which diminished her speed of of cooling, and correspondingly increased the time. Though the problem of the age of the earth as investigated through the changes of her temperature, may not at present becapable of exact solution, it must be admitted that the time required to bring her heat to its present degree must have been inconceivably long.— Harper's Magazine.