Page:The National Geographic Magazine Vol 16 1905.djvu/154



ROF. ERNEST RUTHERFORD contributes to Harper's Magazine for February an intensely interesting article on the cause of the earth's heat, which he is inclined to believe is radium. From his article we may draw much comfort, for whereas Lord Kelvin and later scientists have been arguing that all of our descendants must become extinct in about five million years, Prof. Rutherford gives the hope that our race may hold out for five hundred millions of years, which is quite a bit longer. All estimates, of course, are based on the duration of the heat from the sun. Our new knowledge of radium seems to show that the sun's heat is diminishing much more slowly than has been generally supposed.

After describing the heat inside the earth and the various present theories to account for this heat, Prof. Rutherford proceeds to tell some of the remarkable characteristics of radium.

"In the course of a year one pound of radium would emit as much heat as that obtained from the combustion of 100 pounds of the best coal, but at the end of that time the radium would apparently be unchanged and would itself give out heat at the old rate, and it would emit heat at the above rate for about one thousand years."

The heat which radium gives off seems to be caused by the breaking up of the radium atom into tiny particles, which fly away with tremendous velocity; but notwithstanding their great speed, most

From F. H. Newell, U. S. Geological Survey

Four Coal Beds each 4 or 5 Feet Thick on Little Missouri River, near Mikkelson, North Dakota. See preceding page