204 IIERSCHEL. 



for tlif purpose of ascertainiug the relative distances of clusters of stars, and of inves- 

 tigating how far the iwwer of telescopes maj' be expected to reach into space, when 

 directed to ambiguous celestial objects. 



1822. Memoirs of the Astronomical tSocieiij of London. — On the positions of 145 new 

 double stars. 



The chronological and detailed analysis of so many labors would 

 involve numerous repetitions. A systeipatic order will be preferable, 

 since it more distinct!}' fixes the eminent ijlace that Herschel will never 

 cease to occupy in the small group of contemporary^ men of genius, while 

 his name will reecho to the most distant posterity. The variety and 

 splendor of Herschel's labors vie with their extent. The more we study 

 them the more wo must admire them. It is with great men as it is with 

 great movements in the arts : we cannot understand them without study- 

 ing them from various points of view. 



Let us here again make a general reflection. The memoirs of Herschel 

 are, for the greater part, pure and simple extracts from his inexhaustible 

 journals of observations at Slough, accompanied by brief remarks. Such 

 a table would not suit historical details. In these respects the author 

 has left almost everything to his biographers to do for him. And they 

 must im[)ose on themselves the task of assigning to the great astron- 

 omer's predecessors the portion that legitimately belongs to them out 

 of the mass of discoveries which the public, we must say, are in the 

 habit of erroneously referring too exclusively .'.o Herschel. 



At one time I thought of adding a note to the analysis of each of the 

 illustrious observer's memoirs, containing a detailed account of the 

 improvements or corrections to which the progressive march of science 

 has led. But in order to avoid an exorbitant length in this biog- 

 raphy, I have been obliged to give up my project. In general, I shall 

 content myself with pointing out what belongs to Herschel, referring to 

 Arago's Treatise on Popular Astronomy for the historical details. The life 

 of Herschel had the rare advantage of forming an epoch in an extensive 

 branch of astronomy; it woidd require us almost to write a special 

 treatise on astronomy to show thoroughly the importance of all the re- 

 searches that are due to him. 



IMPKOVBMENTS IN THE MEANS OF OBSERVATION. 



The improvements that Herschel made in the construction and manage- 

 ment of telescopes have contributed so directly to the discoveries with 

 which that observer enriched astronomy that we cannot hesitate to 

 bring them forward at once. 



I find the following passage in a memoir by Lalande, printed in 1783, 

 and forming part of the preface to Volume VIII of the Ephemerides of the 

 Celestial Motions : 



" Each time that Herschel undertakes to polish a mirror (of a tele- 

 scope) he condemns himself to ten, or twelve, or even fourteen hours of 

 constant work. He does not quit his workshop for a minute, not even to 



