POPULAR ASTRONOMY.

Otago Witness, Issue 3098, 30 July 1913, Page 10

POPULAR ASTRONOMY.

THE MARVELS OF THE SUN. The Rev. P. W. Fairclough addressed a meeting of the astronomical branch of the Otago Institute on July 22 on the subject of “New Instruments and Methods in Soiar Research.” Mr R. Gdkisou, the president, occupied the chair, and the attendance may be described as fair. One new member was elected. In his opening remarks the lecturer explained that the great object of solar research was to learn, if possible, how the sun regulated the weather. Subsidiary to tnis was the quest of knowledge as to the relations between the sun and terrestrial magnetism, magnetic storms, and auroras. Speaking of the immensity of the eun, the lecturer stated that 110 earths laid side by side would make a very thin line 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 the stock would supply the sun’s heat for one second. Such appalling facts showed that the sun’s heat could not bo sustained by combustion—that it could not be a solid body, and that it must bo gaseous. Discussing' the problem of how the sun’s heat is sustained, ho showed that it could not bo by the fall of meteors. The theory of Helmholtz now held the field, that the sun was shrinking or falling in upon itself. 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 cf diagrams, explained the central mass, the enveloping photosphere, or light sphere, the general absorption layer, the reversing layer, the chromosphere, the flamoliko prominences of hydrogen, the mysterious pearly corona, only seen at the time of total eclipse, and supposed to be composed of very lino matter in the act of retreating from the sun under the propulsion cf light, and, lastly, the zodiacal light, which was now regarded ns an appendage of the sun, and which extended for, perhaps, 40 or 50 millions of miles into space. After a brief reference to sun spots, the lecturer proceeded to give a most interesting exposition of some of tho more recent methods and instruments employed in solar research. Tho significance of the spectroscope and the heliograph was briefly touched on, and tho lecturer then devoted considerable time, with the aid of models and diagrams, to a most clear and careful explanation of the spcctroheliograph, a new and wonderful instrument of research, the finest example of which was that devised by Professor Hale, of Mount Wilson, in California. Tho means by which the image of the sun is recorded conveniently at the investigator’s table, and how that imago may be examined and photographed in a multitude of ways by tho aid of prisms and the spectrum, and "the vast field of knowledge thus opened up was set forth in the moat entertaining and faicinating manner. R®fore long, the lecturer said, wo might expect to hoar a great deal about the oonstituent elements of the sun through this wonderful piece of mechanism. The Rev. D. Dutton voiced the admiration of members for tho splendidly lucid way in which Mr Fairclough had explained to ‘them this marvellous apparatus. It convoyed to members some conception of the tremendous amount of brain force being employed by the leaders in astronomical science. Others, including tho Chairman, expressed their great appreciation of the lecture. A vote of thanks was accorded to the donor of two valuable books to the society s library.