282 HERSCHEL. 



manner we must endeavour to distinguish separately the 

 two members of certain double stars very close to each 

 other. He said if you wish to assure yourself that i) 

 Coronas is a double star, first direct your telescope to a 

 Geminorum, to ? Aquarii, to p Draconis, to P Herculis, 

 to a Piscium, to e Lyras. Look at those stars for a long 

 time, so as to acquire the habit of observing such objects. 

 Then pass on to Ursas majoris, where the closeness of 

 the two members is still greater. In a third essay se 

 lect i Bootis (marked 44 by Flamsteed and i in Harris s 

 maps) *, the star that precedes a Orionis, n of the same 

 constellation, and you will then be prepared for the more 

 difficult observation of &quot;n Coronas. Indeed n Coronas is a 

 sort of miniature of i Bootis, which may itself be consid 

 ered as a miniature of a Gem. (Philosophical Trans 

 actions, 1782, p. 100.) 



As soon as Piazzi, Olbers, and Harding had discov 

 ered three of the numerous telescopic planets now known, 

 Herschel proposed to himself to determine their real 

 magnitudes ; but telescopes not having then been applied 

 to the measurement of excessively small angles, it became 

 requisite, in order to avoid any illusion, to try some ex 

 periments adapted to giving a scale of the powers of those 

 instruments. Such was the labour of that indefatigable 

 astronomer, of which I am going to give a compressed 

 abridgment. 



* In the selection of i Bootis as a test, Arago has taken the precau 

 tion of giving its corresponding denomination in other catalogues, and 

 Bailey appends the following note, No. 2062, to 44 Bootis. &quot; In the 

 British Catalogue this star is not denoted by any letter: but Bayer 

 calls it&quot;, and on referring to the earliest MS. Catalogue in MSS. vol. 

 xxv., I find it is there so designated; I have therefore restored the 

 letter.&quot; (See Bailey s Edition of Flamsteed s British Catalogue of 

 Stars, 1835.) The distance between the two members of this double 

 star is 3&quot; -7 and position 23 -5. See &quot; Bedford Cycle. 1 Translator. 



