42 



SCIENTIFIC NEWS. 



[Jan. 13, 1? 



ABSTRACTS of PAPERS, LECTURES, etc. 



ROYAL INSTITUTION. 



The Sun. 

 The Christmas lectures, adapted to a juvenile auditory, 

 were given this season by Sir Robert Ball, Astronomer 

 Royal of Ireland, who commenced the series with a 

 discourse about the sun. He spoke of the heat 

 and brightness of the sun, and of its immense im- 

 portance to us, though it was not the largest body in the 

 universe. Lantern views were thrown upon the screen, 

 representing instruments used in astronomy, from the 

 apparatus of Tycho Brahe to the great Vienna telescope 

 and the telescope of Lord Rosse. The telescope of the 

 Dublin Observatory, with an object glass twelve inches 

 in diameter, had been considered to be at the head of its 

 class until lately, when there had been an international 

 competition to possess the largest. America obtained a 

 larger one, and then the Austrian Government deter- 

 mined to possess one larger still, and the telescope at 

 Vienna, made in Dublin, had a glass of twenty- 

 seven inches in diameter. Now, he remarked, the 

 Greenwich authorities, resolving not to be behind, had 

 ordered a telescope from Dublin which should be bigger 

 than the great Austrian telescope. Sir R. Ball referred 

 to the recent bright appearance of Venus, which so many 

 persons persuaded themselves was the " Star of 

 Bethlehem," appearing only once in 300 years. He did 

 not know what had set this extraordinary story going, 

 but as Venus appeared as a morning or evening star once 

 in a year and seven months, it followed that it must 

 sometimes be seen in that capacity at Christmas time, 

 and he supposed that that fact had acted on people's 

 imagination. The alternation of day and night, and the 

 long arctic day and night, were demonstrated, and sun 

 spots were exhibited on the screen in great variety, and 

 their nature explained. In conclusion, the lecturer, 

 pointing to a globe ten inches in diameter, taken to re- 

 present the sun, held beside it a shot. No. 5, which 

 showed the comparative size of the earth. 

 The Moon. 

 In the second lecture, after having presented a picture 

 of the surface of the moon as revealed by the telescope 

 when viewed in the form known as full moon, the lec- 

 turer proceeded briefly to impart to his young hearers 

 such information with regard to its form and substance 

 as has been gained by means of the telescope and 

 photography. It was 2,000 miles across, and evidently 

 of volcanic origin. So far away was our satellite that 

 even if it produced elephants as large as cathedrals they 

 would appear to us no larger than mites moving about ; 

 but there was good reason to conclude that there was no 

 life upon the surface of the moon. Sir Robert Ball then 

 explained the phases of the moon, and showed, by 

 means of globes exposed to the electric light, how it was 

 that the moon appeared sometimes " full," and some- 

 times " new." By a similar method of illustration the 

 lecturer explained the reason why the planet Venus 

 shines with so brilliant a light just before sunrise or after 

 sunset. He touched upon the eclipse phenomenon, and 

 showed a number of pictures and diagrams illustrating 

 the character of the moon's surface. Among these were 

 the Platfo crater and other extinct volcanos which have 

 been carefully mapped by astronomers. The presence 

 of ocean beds was also demonstrated, and it was ex- 

 plained that, many ages yet to come, it was possible that 



the vvaters of the earth might in like manner be dried 

 up, and the beds of the ocean remain to tell the tale to 

 the inhabitants of other planets. The relative sizes of 

 the earth and the moon were next considered, and by 

 means of red-hot globes of iron the process of cooling 

 was illustrated. A model of a lunar crater was also 

 exhibited, and the method of measuring the heights of 

 the mountains and the diameters of the craters was ex- 

 plained. 



The Small Planets. 

 Sir Robert Ball in the third lecture dealt with 

 the small planets embraced within our solar system. 

 After explaining at some length the theory of gravitation, 

 and showing how the sun controlled the movements of 

 the various celestial bodies included in his system, the 

 lecturer elucidated the way in which the planets derived 

 the light which renders them so conspicuous at night, 

 while by day they are not distinguishable. Diagrams 

 were shown in which the relative sizes of the great and 

 small planets were set forth and the nature of their 

 orbits illustrated. The varying character of the move- 

 ments of Me rcury, Venus, andtheearth were also portrayed, 

 and the different periods at which the planets appeared 

 to cross the sun's disc were fully explained. The phases 

 of Venus were graphically illustrated by the aid of the 

 electric light, and again referring to the recent speculation 

 concerning the Star of Bethlehem, the lecturer remarked 

 that, notwithstanding all that had been said and written, 

 he was continually being asked by anxious inquirers as 

 to whether Venus was the identical star in question or 

 not. Sir Robert Ball then proceeded to illustrate the so- 

 called transits of Venus, and showed why so much 

 anxiety was displayed by astronomers to observe the 

 phenomenon on those rare occasions when it occurred,and 

 the difficulties under which their observations had to be 

 conducted. Oneimportantresult which wasobtainable from 

 an accurate observation of the transit was a reliable esti- 

 mate of the actual distance which separated the earth from 

 the sun ; and without being particular to an inch or two, 

 astronomers had been enabled to fix the interval at 

 92,700,000 miles. The lecturer then explained the 

 varj'ing seasons of the earth as caused by the inclination 

 of its axis, which was duly illustrated by experiment. 

 Another experiment which occupied some time was the ex- 

 planation by means of Foucault's pendulum of the revolu- 

 tion of the earth. Some diagrams of Mars were shown, 

 and in reference to the curious parallel lines mapped by 

 Schiaparelli, Sir Robert Ball remarked that many 

 theories had been advanced by way of explanation. 

 Among others, it had been suggested by a citizen of 

 Manchester that no doubt one line represented a railway 

 between two commercial centres, while the parallel was 

 formed by an opposition canal. The two satellites of 

 Mars were also shown, and, alluding to the fact that one 

 of them revolved round the planet once every seven and 

 a half hours, the lecturer drew attention to the fact that 

 in " Gulliver's Travels " Swift had represented the 

 philosophers of Laputa as having discovered that Mars 

 had two satellites, one of which revolved its course in nine 

 hours. This was put forth as a ludicrous idea, but truth 

 had actually proved stranger than fiction. 



GEOLOGICAL SOCIETY. 

 On December 7th, 1887, the communications read 

 were : — 



I. "A Letter from H.M. Secretary of State for the 



