THE LIGHT AND HEAT OF THE SUN.

Southland Times, Volume III, Issue 247, 27 April 1866, Page 3

THE LIGHT AND HEAT OF THE SUN.

SUN. (From the London Eevietp.) Whilst the different arguments for and against KirehofFs theory for the constitution of the fsun are being discussed in our pages, it may interest our readers, and possibly also assist in the settlement of the debated questions, if we draw attention to some speculations respecting the source of light and heat of the sun, which have been of late years reduced to numerical computation by Professor Thompson. The hypothesis was, we beI lieve, originated by Mr "Waterston, who propounded the idea that the solar light and heat are produced by the impact of a shower of meteoric or small • planetary bodies, continually falling from the surrounding space into the atmosphere or on to the surface of the sun. Heat results from the stoppage of mechanical force, in amount equivalent to the mechanical effect of that force, and it has been fully proved by Professor Thompson that the amount of heat evoved by the fall of a meteor into the sun, striking on its surface with a velocity which, cannot be less than 400 miles in a second of time, would instantly generate, and flash into space an enormous amount of heat and light. A similar effect takes place when a shooting star falls on to the earth with a vastly less velocity. The momentum being checked on entering the earth's atmosphere, its vis viva is converted into heat, which is frequently of sufficient intensity to melt and dissipate the matter into fragments too small to be noticed when they reach the ground. Assuming, with most astronomers, that the zodiacal light is net ling but a ring of meteors surrounding the sun, the whole of the sun's heat is accounted for on the supposition that this annular appendage i 3 constantly yielding a meteoric rain to the •sun's surface. It may at first seem a valid objection to this theory, that this constant accumulation of new matter on the surface of the sun would augment its diameter; but, granting this to be the case, it has been shown that the entire amount of heat and light evolved from the sun, during a whole year, would be realised by the fall of meteors, which would increase its diameter by only sixty feet. To telescopic observers, this would only increase the angular diameter of the sun by one second in 40,000 years ; an amount which could scarcely be detected by our present means of observation; whereas, on the supposition that the sun's light and heat are produced by combustion or electricity, at least three thousand times the above quantity of matter would require to enter annually into chemical combination at the sun's surface. Respecting the actual temperature of the sun's surface at the present time, Professor Thompson remarks that it cannot be incomparably higher than temperature attainable artificially at the earth's surface. The heat radiated from every square foot of his surface is equiralent to 7000 horse-power, or an amount equal to that generated by coal burning at the rate of a little less than a pound in two seconds of time. As in locomotive engines one pound of coal is burned in from thirty to thirty-nine seconds per square foot of grate-bars, it follows that the heat is radiated from the sun at a rate not more than from fifteen to forty-five times as hight as that at which heat is generated on the grate-bars of a locomotive furnace, with equal areas. "We have already given an outline of the meteoric theory of the origin of solar heat. According to Professor Thompson, this is the only theory which, in the form in which it has been advocated by Helmholtz, is adequate, consistently with natural laws, to account for the present position of the sun, and for radiation continued at a very slowly decreasing rate during many years past and future. "We may, indeed, suppose that the sun may have been created an active source of heat at some time of not immeasurable antiquity, by an over-ruling decree ; but, without pronouncing this supposition to be essentially incredible, Professor Thompson assumes that it may be safely said to be in the highest degree impossible, if, as he believes to be the case, we can show the meteoric theory to be not contradictory to known physical laws. But neither this nor any other natural theory can account for solar radiation continuing at many hundred millions of years. "It seems, "therefore," says Professor Thompson, "on the whole most probable that the sun has illumined the earth, for 100,000,000 years, almost certain tha.t he has not done so for 500,000,000 years. As for the future, we may say with equal certainty, that the inhabitants of the earth, cannot continue to enjoy the light and heat essential to their life for many million years longer, unless new sources, now unknown to us, are prepared in the great storehouse of Creation."

An Irish girl told her lover, wioni her friends had denied admittance to the house, that she was anxious to possess his portrait, and intended to obtain ;+ -. " But how if your friends see it B" he inquired. " Oh, I'll teU the artist not to make it like you, and then they won't know it !/ The latest fashion in Paris is for ladies to be accompanied, in the drive or promenade, by immense dogs. C»3 lady attracts great attention on account of a monster which follows her about. Ifc is almost like a young pony, and imported from Wurtemburg, whjgr^ t.h.6 t&CQ is. &e»r!y $xtip,et v