Radio-activity has a vivid interest far beyond the laboratories of chemists and physicians. One of the long standing puzzles of geology has been to explain why the temperature of the earth has remained fairly constant ever since organic life made its appearance. A sister problem has been the maintenance by the sun of its vast output of heat and light, age after age, with little or no diminution of intensity. Professor Rutherford and Mr. Soddy believe that the phenomena of radio-activity may solve both these problems: an element like helium may furnish a store of energy vastly greater than that of ordinary chemical action, and much lengthen the cooling process due to radiation from either the sun or the earth. Radio-activity, furthermore, throws new light upon evolution regarded in its broadest aspects. The corpuscles discovered in 1897 by Professor J. J. Thomson, as he severed atoms in pieces, are all alike whatever chemical element may be the parent body. Hence it is argued that we may have here the primal units of all matter whatever. Sir Norman Lockyer long ago pointed out that helium and hydrogen predominate in the hottest stars, while in stars less hot more complex types of matter appear. He argues that these stars as they successively lose heat show a development of what chemists call elements. His views are parallel with the suggestion that in the radio-active corpuscle we make acquaintance with an ultimate element of all matter, whether observed in a laboratory tube or in the squadrons bright of the midnight heavens.[22] [22] Radio-activity and other physical phenomena recently discovered are set forth in “The New Knowledge,” by Professor Robert Kennedy Duncan, published by A. S. Barnes & Co., New York, 1905; and “The Recent Development of Physical Science,” by W. C. D. Whetham, published by John Murray, London, and P. Blakiston, Son & Co., Phila., 1906. The phenomena of radio-activity revive interest in the prophetic views of Michael Faraday. In 1816, when he was but twenty-four years of age, he delivered a lecture at the Royal Institution in London on Radiant Matter. In the course of his remarks there occurs this passage:-- Faraday’s Prophetic Views. “If we now conceive a change as far beyond vaporization as that is above fluidity, and then take into account the proportional increased extent of alteration as the changes arise, we shall perhaps, if we can form any conception at all, not fall short of radiant matter; and as in the last conversion many qualities were lost, so here also many more would disappear.