SIR JOHN FREDERICK WILLIAM HERSCHEL. 129 



The real work of the Herscliels, then, that to which all their labors 

 were directed, was the survey of those regions of space which lie beyond the 

 range of the unaided vision. Other work they did which well deserves 

 attention. Sir William Herschel, in particular, left papers describing- 

 observations of the planets, careful studies of the sun's surface, and 

 researches into a variety of otiier subjects of interest. But all the 

 work thus recorded was regarded by him rather as affording practice 

 whereby he might acquire a mastery over his instruments than as a work 

 to which he cared to devote his powers. Even the discovery of a planet 

 traveling outside the path of Saturn — although, in popular estimation, 

 this discovery is regarded as the most note-worthy achievement of Her- 

 schel's life — was in reality but an almost accid-^^ntal result of his real 

 work among the star-depths. It was, in truth, such an accident as he 

 may be said to have rendered a certainty. iJ^o man can apply the pow- 

 ers of telescopes, larger than any before constructed, to scrutinize as he 

 did every portion of the celestial depths, without being rewarded by 

 some such discovery. He never swept the star-depths for an hour with- 

 out meeting multitudes of hitherto unknown orbs, far mightier than the 

 massive bulk of Uranus. These discoveries pass unrecorded save nu- 

 merically, but they tended to the solution of the noblest problem which 

 men have yet attempted to master. It was the same with the sou. All 

 discoveries, all studies, w^ere subordinated to this one purpose, « A'«oh;Z- 

 edge of the eonstruction of the heavens. 



In the pursuit of this single end it is not strange that the great pio- 

 neer of star-observers should have formed opinions irom time to time 

 which he afterwards abandoned as unsupported by facts. In his paper, 

 printed in the Philosophical Transactions of 1785, Sir William Herschel 

 had said, " I have now viewed and gauged the milky way in almost 

 every direction, and find it composed of stars whose number constantly 

 increases and decreases in proportion to its apparent brightness to the 

 naked eye. That this shining zone is a most extensive stratum of stars 

 of various sizes admits no longer of the least doubt, and that our sun 

 is actually one of the heavenly bodies belonging to it is evident." In 

 the plate accompanying this paper, our sun makes one of innumerable 

 stars, all comparable with each other in magnitude, and distributed with 

 approach to uniformity. 



In 1802, after his telescope had been asking seven years longer the 

 secret of the skies, writing of our sun, magnificent as its system is, as 

 only a single individual of the insidated stars, he says: "To this may 

 be added that the stars we consider as insulated are also surrounded by 

 a magnificent collection of innumerable stars called the milky way. 

 For, though our sun and all the stars we see may truly be said to be 

 in the plane of the milky way, yet I am now convinced by a long in- 

 spection that the milky way itself consists of stars differently scattered 

 from those which are immediately about us." 



Similar changes of opinion in regard to the nature of double stars, 

 y s71 



