In the first place, we both take as our fundamental basis of speculation the idea of an universal extension of atmospheric matter, and we both regard this as the recipient of the diffused solar radiations, which are afterwards recovered and recondensed, or concentrated. Thus our “fuel of the sun” is primarily the same, but, as will presently be seen, our machinery for feeding the solar furnace is essentially different. Certain desiccated pedants have sneered at my title, “The Fuel of the Sun,” as “sensational,” and have refused to read the book on this account; but Dr. Sterry Hunt has provided me with ample revenge. He has disentombed an interesting paper by Sir Isaac Newton, dated 1675, in which the same sensationalism is perpetrated with very small modification, Sir Isaac Newton’s title being “Solary Fuel.” Besides this, his speculations are curiously similar to my own, his fundamental idea being evidently the same, but the chemistry of his time was too vague and obscure to render its development possible. This paper was neglected and set aside, was not printed in the Transactions of the Royal Society, and remained generally unknown till a few months ago, when the energetic American philosopher brought it forth, and discussed its remarkable anticipations. Dr. Siemens supposes that the rotation of the sun effects a sort of “fan action,” by throwing off heated atmospheric matter from his equatorial regions, which atmospheric matter is afterwards reclaimed and passed over to the polar regions of the sun. This interchange he describes as effected by the differences of pressure on the fluid envelope of the sun; the portion over the polar regions being held down by the whole force of solar gravitation, while the equatorial atmosphere is subject to this pressure, or attraction, minus the centrifugal impulse due to solar rotation. He maintains that this “centrifugal action, however small in amount as compared with the enormous attraction of the sun, would destroy the balance, and determine a motion towards the sun as regards the mass opposite the polar surface, and into space as regards the equatorial mass.” He adds that “the equatorial current so produced, owing to its mighty proportions, would flow outwards into space, to a practically unlimited distance.”