70 Dr. Herschel on the Power of 



of the planet, a different sort of power, namely, that of magni- 

 fying, was required ; and, about the time of its discovery, I had 

 been remarkably attentive to an improvement of this power, as 

 I happened to be then much in want of it for my very close 

 double stars.* 



On examining the nebulaa which had been discovered by 

 many celebrated authors, and comparing my observations with 

 the account of them in the Connoissance des Temps for 1 783, I 

 found that most of those which I could not resolve into stars 

 with instruments of a small penetrating power, were easily 

 resolved with telescopes of a higher power of this sort ; and, 

 that the effect was not owing to the magnifying power I used 

 upon these occasions, will fully appear from the observations ; 

 for, when the closeness of the stars was such as to require a 

 considerable degree of magnifying as well as penetrating power, 

 it always appeared plainly, that the instrument which had the 

 highest penetrating power resolved them best, provided it had 

 as much of the other power as was required for the purpose. 



Sept. 20, 1783, I viewed the nebula between Flamsteed's 

 99th and 105th Piscium, discovered by Mr. Mechain, in 1780. 



" It is not visible in the finder of my 7-feet telescope; but 

 " that of my 20-feet shews it." 



Oct. 28, 1784,, I viewed the same object with the 7-feet tele- 

 scope. 



" It is extremely faint. With a magnifying power of 120, it 

 " seems to be a collection of very small stars : I see many of 

 " them/' 



* Magnifying powers of 460, 625, 932, 1159, 1504, 2010, 2398, 3168, 4294, 

 5489, 6450, 6652, were used upon e Bootis, y Leonis, « Lyrre, &c. See Cat. of double 

 stars, Phil. Trans. Vol. LXXII. page 115, and 147 ; and Vol. LXXV. page 48. 



