THE StJN

Evening Post, Volume CV, Issue 124, 28 May 1928, Page 6

THE StJN

«, , • ■ A W.E.A. LECTURE Tho Bed Cross Hall in Dixon street was well-filled on Saturday evening, when Professor D. M. Y. Sommcrville, of Victoria University College, continued fhis short, course in astronomy for the W.E.A., and delivered an instructive address on "The Sun." Next to the earth, said the lecturer, tho sun was i for us' by far-the most important body in tho universe, as it was ' the source of all our light and heat, and everything that makes life possible. It was the ultimate source also ofj all artificial supplies of heat and light, for it was the sun's action in the past that caused the trees to grow, which in ancient times became converted into. coal. It was the sun's heat which raised water by evaporation and caused rivers, which wo used for hydro-electric sys- '. terns. '„ The measurement of the distance of the sun was a problem which had greatly occupied the attention of astronomers, as it formed really the standard measuring rod for the universe. The early attempts to measuro this accurately were based on the'transits of Venus, which occur only at rare intervals. The transit of 1769 was of especial interest in connection with Captain Cook and tho Royal Society Expedition, an event which left i ( ts mark in tho name of the Society Islands, and Point Venus in Tahiti, where the transit'was observed. In tho same , year Captain Cook, when in New Zealand, observed a transit of Mercury, commemorated in the name Mercury Bay. Other methods of finding tho sun's distance were ;based on measurements of tho distances of Mars ana some of tho minor planets;'; which, 'sometimes make a near approach to ■ the earth. A close approach of the small planet Eros will^be useel for this purpose in 1931. . . The density of the sun showed that it is-liquid or gaseous.' Our knowledgo of its constitution was obtained1 almost ■ entirely by means of the. spectroscope. ■This revealed the presence in. the sun's atmosphere of most of the common* elements found on the. earth.' 'in ,1868 Lockyer discovered a hitherto unknown element, to which was given the muno helium, and which was found afterwards by Bamsay as a rare gas. It is ' now obtained from natural sources in large quantities, and is used in America instead of hydrogren for filling airship balloons. " . ::,;./ "The study: of:.sHnsj)ots'-;;aud>,their periodicity is^l^;il|^ta;^(littv:tim]rcirtant developinen^a';'jJn<;^/Metboroi6gy: ,' >' said Professor Sommefville. "There is a well-marked relation between sunspots and terrestrial magnetism, and it is thought that seasonal changes in climate may also be connected with the sunspot period, though they are masked by a multitude of other effects. Of the actual nature of sunspots and the corona as yet little is known. The great advances which the science of physics has made in recent years point to some of the problems' which have to bo attacked, but our present knowledge is only sufficient to reveal our ignorance." The lecture was illustrated by a series of fine lantern slides. At the conclusion of the nddrcss a number of questions wore nsked. Next Saturday night Professor Sommervillo will deal with "The Solar System."