1888.] President'' s Address. xxxv 



chiefly because more of the details of its surface are visible than is 



the case with the others. This is due partly to its proximity to the 



earth, but chiefly to the tenuity of its atmosphere. It must be rare 



to admit of these details being seen and yet judging from the 



behaviour of what are supposed to be polar snows or ice, the climate 



seems to be unexpectedly mild. How these apparently contradictory 



facts are to be reconciled I do not know. In 1877 August a memorable 



discovery was made by Prof. Asaph Hall with the 26-inch refractor 



at Washington, viz., that Mars was the possessor of two small moons. 



And very interesting little bodies these are : — assuming that they 



reflect the same proportion of the Sun's light that Mars does, they are 



. about 6 and 7 miles respectively in diameter, the inner one being the 



larger. This inner one revolves round its primary in 7^. 29'". at a 



distance from its surface of only 3,760 miles, and we are here 



presented with the unique case of a satellite completing its revolution 



in less than its primary's day and coming to the meridian twice or even 



ithree times in that day. At this same opposition of 1877 Sehiaparelli 



had observed that what had always been called the continents of Mars 



were really a collection of islands connected by long markings of about 



' 60 miles in breadth which have been called " canals." These were 



distinctly visible again from 1881 December to 1882 February, but 



in many cases were seen to be doul^le, i.e. another canal was found 



parallel to the original one ; and this dciplication has been verified 



in 1886 and the present year. Travelling farther from the Sun we 



come to the group of asteroids which have now become so numerous 



that they require the whole attention of a separate department at 



Berlin to follow their movements and guard against their being lost. 



The last discovered was number 278 I believe. Naturally the ones 



recently discovered are on the average fainter than the earlier ones ; 



they average about 11 or 12 magnitude and are jtrobably not more 



than 15 miles in diameter. 



The chief modern discovery about Jupiter is that he is in a stage 



«midway between the Sun and the Earth ; he has not cooled dowa 



^sufficiently to possess a solid crust, and his vast stores of internal heat 



give rise to agitations which are shewn by the changes observed in 



his disc. This discovery however does not belong to the period we a^e 



considering. In 1878 Pritchett, Director of the Morrison Observatory 



(U.S.), observed an enormous rosy cloud near the southern equatorial 



band ; and in 1879 and the two following years the Grreat Red Spot, 



^s it was called, attracted universal attention. Its cclour had deep3ned 

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