THE magnitude of the coal industry is indicated by the fact that the world's production of coal exceeds the enormous total of 1,000,000,000 tons per annum, while about 4,000,000 persons find employment in or about coal mines. The importance of the coal industry is second to none. The utilization of the heat and energy derived from the combustion of coal has been a dominating influence in the progress of the world during the past century, and it has been said that it has done "more to change the mode of life and habits and thoughts of mankind than has been effected by all political, social, and personal influences combined, and" unless new methods of obtaining power are discovered, the future progress of civilization depends on its supply of coal and other fuels." It is within the range of possibility, although it seems almost chimerical in the present state of our knowledge, that the recently discovered radio-activity may play an important part in power-production centuries hence. Its possibilities are enormous. It is said that an ounce of radium liberates, in its transmutation into other kinds of matter, as much energy as is produced by the combustion of about 7 tons of coal; but it takes 2000 years to do this by the present process of natural decay, and up to the present no method of hastening or retarding this evolution of energy has been found.