Recently a mechanism allowing the escape of the heat generated by radioactivity in the basaltic under-crust of the earth has been proposed by Dr. Holmes, and a very similar one by Dr. Joly has gained wide attention. In these theories the excess heat generated by radioactive changes is supposed to be dissipated by an alternate fusion and solidification of the basaltic magmas assumed to make up the lower levels of the outer crust, the heat escaping through the floor of the oceans during so long a period of time that while, in the aggregate, the amount of heat thus passed out is very great, yet at no time is the temperature of the oceans sensibly affected.