SIR DAVID GILL, ON THE SIDEREAL UNIVERSE. 185 



that it has already conquered, bidden us to look out over the lands 

 into which we may hope in the future to advance. I think that one 

 of my own earliest astronomical recollections is that of meeting 

 Sir David Gill before he set out with the Earl of Crawford, then 

 Lord Lindsay, to observe the Transit of Venus of 1874. From 

 that time to the present the science of astronomy has been advanced 

 by the efforts of no one more effectually than by his; and in 

 particular he has devoted himself to the solution of the great 

 problems of the celestial distances ; of the determination of the 

 scale upon which the starry heavens are built. And the great 

 fundamental unit of astronomical distance is necessarily the distance 

 of the earth from the sun. To this Sir David devoted himself with 

 unswerving determination, and infinite resource. He followed up 

 the method of observation of the Transit of Venus, by that of 

 heliometer measures of Mars at the opposition of 1877, and then by 

 observations of various minor planets ; Iris, Sappho and Victoria. 

 At that time it seemed an almost preposterous supposition that the 

 distance of the sun could be determined by the means of the 

 spectroscope ; through measures of the rate of motion of the earth 

 in the line of sight, relative to various stars ; the rate of motion 

 either of recession or approach. Yet absurd as the idea then 

 seemed. Sir David grasped the possibilities of the method and 

 did not hesitate to predict its success, and his faith has been 

 abundantly justified by the result ; largely through work which he 

 himself initiated and arranged at the great observatory over which 

 he ruled for eight and twenty years. But this fundamental problem 

 of the distance of the sun was only one of those to which he devoted 

 himself. The distances of certain stars were measured by him, and 

 he was one of the most strenuous and influential movers in setting 

 on foot the photography of the heavens, some of the latest fruits of 

 which we have seen in the beautiful slides that he has exhibited 

 to us this afternoon. It is now nearly thirty years since the great 

 comet of 1882 flared into our skies. Sir David had a number of 

 fine photographs of that object taken at the Cape Observatory, and 

 from the number and distinctness of the star-images shown on those 

 plates, drew the inference that in photography we had the means 

 for obtaining a fuller and more complete record of the heavens than 

 direct eye-observation alone could ever give. He was therefore 

 urgent in pressing the claims of the new method upon astronomers, 



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