206 



♦ KNO^A^LEDGE ♦ 



[July 1, 1887. 



forms the image of the object, we see that the defining 

 powers as indicated in the study of close double stars, must 

 determine also the comparative powers of telescopes in show- 

 ing the details of the surfaces of sun, moon, planets, comets, 

 and star clouds. 



There can be no doubt whatever of the potential value 

 of very large telescopes. If we could estimate the value of a 

 telescope simply, without regarding the man at the small 

 end of it (stay : with reflecting telescope we find him some- 

 times at the large end), we could have no doulit as to the 

 desirability of settmg our C'larkes and Grubbs and the rest 

 of them making the largest telescopes money can buy. But 

 if we are to judge by the experience of the last twelve or 

 fifteen years, we must infer that very large telescopes may 

 fail in actual service, even as the great two-handed swords 

 of the Swiss failed in the hands of warriors effectively skilful 

 in the use of less unwieldy weapons. {Teste Arthur Phillip- 

 son in " Anne of Geienstein.") 



The first example which occurs to me is that of an 

 esteemed friend of mine in England. Nothing could have 

 been more admirable than the way in which he worked 

 alike with telescope and spectroscope, and with both com- 

 bined, when he possessed only an eight-inch telescope. 

 Every one expected that when a convertible fifteen and 

 eighteen-inch telescope was placed at his disposal by the 

 Royal Society he would effect correspondingly enhanced 

 achievements in the way of discoveiy and research. But 

 all the work done by him with the large telescope during 

 the last twelve years is much more than outweighed by his 

 work in 1864 alone with the small one. 



In America examples are more numerous simply because 

 a much greater number of large telescopes has been erected 

 here. (Newall's and Buckingham's large telescopes in 

 England were such utter failures that one is moved by pity 

 not to touch on their achievements — at least, one would be 

 if there were any achievements to touch on.) Tliere was 

 the great telescope at Chicago, an 18-inch of Alvan Clarke's 

 best workmanship. Beyond enabling Burnham to test the 

 value of the double-star observations he had made with a 

 much smaller instrument, this splendid telescope has done 

 nothing. A treatise on astronomy which mentioned nothing 

 discovered with the gi'eat Chicago telescope, or with the 

 equally large telescope set up at Charlottesville, near 

 Richmond, would be certainly none the worse for the 

 omission. 



One cannot say this of the great telescope at Washington, 

 because no treatise on astronomy would be complete which 

 did not mention the two moons — if moons they should be 

 called — of the planet once called by Tennyson the " moon- 

 less Mars." Undoubtedly the discovery of these two bodies 

 was an interesting achievement. Their very minuteness, 

 though detracting from their importance, adds to theii* 

 interest, and also of course made their discovery more 

 difficult. They may not be moons in the sense in which 

 such oi'bs as our own moon and the moons of Jupiter are 

 so called ; for the two together would probably make but 

 about one-milHonth part of our own moon's volume. But 

 they have enabled astronomers to correct their measure of 

 Mars's mass, and they have suggested most instructive 

 thoughts as to the probable processes by which the Martian 

 S3-stem was formed. The great telescope at Washington 

 will always be honourably remembered and Professor Hall 

 always gratefully mentioned in connection with the dis- 

 covery of these tiny bodies. Yet, regarded as a telescopic 

 achievement, this sole work of the great 2G-inch telescope 

 (except two or three fairly good drawings of Saturn by 

 Trouvelot, some mediocre pictures of Jupiter and an 

 " atrocity " by Mr. E. S. Holden, claiming to represent 

 the great nebula in Orion) can hardly be esteemed impres- 



sive. It would have been very discreditable if the moons 

 of Mars had escaped discovery by an instrument which, it 

 now appears, has ten times the light-gathering power neces- 

 sary to show them even under much less favoui-able con- 

 ditions than existed in August 1877, when they were 

 discovered. True, many very powerful telescopes which 

 ought to have discovered the Martian moons, had been 

 turned on Mars without showing them. Had the Wash- 

 ington telescope failed, as used by Professor Hall, tlie 

 discredit of the failure would have had to be so widely 

 shared that it would not have amounted to much. True, 

 also, that there is nothing new in the recognition of different 

 objects with small telescopes after they have been discovered 

 by large ones, and when the observer knows just where to 

 look for them. (My friend Mr. Ward, of Belfast, can 

 actually see two of the moons of Uranus with a 4-inch 

 telescope.) But neither circumstance can take away from 

 the fact that both the moons of Mars were easily within 

 range of the great telescope at Washington when discovered, 

 and that they could only be missed through such careless- 

 ness of survey as unfortunately had been usual in all former 

 search for Martian satellites. 



Probably Professor Hall would be the last to compare his 

 discovery of these two bodies with William Herschel's dis- 

 covery of two moons of Uranus, reniembering how in his 

 own case a splendid telescope had been constructed for the 

 work by the ablest opticians living, whereas Herschel made 

 his own telescope, while also — a circumstance not dwelt on 

 quite so much, I think, as it should have been — Herschel had 

 not only made the telescope with which he discovered the 

 moons of a remote planet, but had begun the work by first 

 discovering the planet itself on which those moons attend. 



I do not care to dwell on the most striking example (in 

 America) of the disappointment apt to result from the con- 

 struction of .a very large telescope for use by an astronomer 

 who has achieved important success with a small one. It 

 has been my special pleasure to dwell on the successes of 

 American astronomers. These even now do not receive 

 nearly the amount of attention in the old country that they 

 merit, and are often treated most unfairly, as in the case of 

 the admirable work of the astronomer whose loss science 

 still feels — my valued friend, the late Dr. Henry Draper. 

 American astronomical researches were scarcely noticed at 

 all- in England till I directed special attention to them, inso- 

 much that an eminent English man of science, somewhat 

 exaggerating, once spoke of me as having " discovered 

 American astronomy " for my fellow-countrymen. It would 

 therefore not be agreeable to me to dwell on disappointments 

 in a case where my own expectations and the hopes of 

 American men of science had been highest. But it is 

 certain that what I have said of our ablest telespectroscopist 

 in England may be matched — and I fear more than matched 

 — by what might be said of the ablest telespectroscopist in 

 America. With a telescope of tenfold greater power he has 

 achieved less in the last ten years * than in any one of the 

 ten years or so preceding them. 



When I am asked, then, what science may hope or expect 

 from the great telescope of the Lick Observatory, I feel con- 

 strained to reply that, judging from recent experiences, we 

 can hardly expect aught but disappointment, though we may 

 hope (" hope springs eternal in the human breast ") for 

 better things. Let science comfort herself with the thought 

 that at least no Young or Huggins will be expended vainly, 

 judging from present appearances, in the attempt to make 

 the big telescope a great success. This at any rate is some- 

 thing, though it would count for more if some despotic 



* The telescope has only been actually at work about six years, 

 it seems. 



