POPULAR ASTRONOMY.

Otago Daily Times, Issue 15823, 23 July 1913, Page 8

POPULAR ASTRONOMY.

THB MARVELS OF THE SUN

Tho Itqv. I'. W. Fairclough addressed it meeting ot tiie astronomical branch of the Utugo institute last night, oil the subjcct of "Auw Instruments and Methods in Soar Itceearch." Mr 15. Uilkison, the president, occupied the chair, and the attendance may he described as fair. One new member was ctoctcd.

In his opening remarks the lecturer explained that the great object of solar research was to loarn, if possible, how the sun regulated the weather. Subsidiary to this was the qutst of knowledge as to the relations between the sun and terrestrial magnetisiA, magnetic storms, and auroras. Speaking of the immensity of tho sun, the lecturer stated that 110 earths laid side by side would make a very thin L'no across its surface. The whole earth did not intercept more than one 200 millionth of the sun's total output of heat. If the coal mines of the earth was to accumulate their output at the present rate for 40 million veais tho stock would supply the sun's heat for one second. Such appalling facts that the sun's hea.t could not be sustained by combustion—that it could not -be a. c-ohd body, and that it must be gaseous. Discussing the problem of how the sun's heat is sustained, he showed that it could not be by the fall of meteors. The theory of llelmholtz now held the field, that the sun was shrinking or falling in upon itseli. The discovery of vast masses of helium—a product of radium—made it possible that this marvellous element might be an important factor in maintaining the solar radiation. Coming to the constitution of the sun, the lecturer, with the aid of diagrams, explained tho central mass, the enveloping photosphere, or light sphere, the general absorption layer, the reversing layer, the chromosphere, the flainelike prominences of hydrogen, the mysterious pearly corona, only seen at the time of total eclipse, and supposed to bo composed of very fine matter in the act of retreating from the sun under tho propulsion of light, and, lastly, the zodiacal light, which was now regarded as an appendage of the sun, and which extended for, perhaps, 40 or 50 millions ot miles into space. After a brief reference .to sun spots, the lecturer proceeded to give a most interesting exposition of some of tho moro recent methods and instruments employed in solar research. The sisnifiamce of the spectroscope and the heliograph was briefly touched on, and the lecturer then devoted considerable time, with the aid of models and diagrams, to a. most clear and careful explanation of the spectroheliograph, a new and wonderful instrument of research, the finest example of which was that devised by Professor Hale, of Mount Wilson, in California. The means by which the image of the sun'is recorded conveniently at the investigator's table, and how that image may be examined and photographed in a multitude of ways by the aid of nrisms and the spectrum, and the vast field of knowledge thus opened up ivas set forth in the most entertaining and fascinating maimer. Before long, the lecturer said, we might expcct to hear a. great deal about tho constituent elements of the sun through this wonderful piece of mechanism. The Rev. D. Dutton voiced the admira : tion of members for the splendidly lucid way in which Mr Fairclough had explained to "them this marvellous apparatus. It con-' veyed to members some conception of the t-reinondoiw aniount of brain force being employed by the leaders in astronomical

Others, including the Chairman, expressed their great appreciation of the lecture. A voto of thanks was accorded to the donor of two valuable books to tbc society's library.