penetrating into Space by Telescopes. 77 



Among other instances of the superior effects of penetration into 

 space, I should mention the discovery of an additional 6th satel- 

 lite of Saturn, on the 28th of August, 1 789 ; and of a 7th, on the 

 1 ith of September, in the same year ; which were first pointed 

 out by this instrument. It is true that both satellites are within 

 the reach of the 20-feet telescope; but it should be remembered, 

 that when an object is once discovered by a superior power, an 

 inferior one will suffice to see it afterwards. I need not add, that 

 neither the 7 nor 10-feet telescopes will reach them; their 

 powers, 20 and 29, are not sufficient to penetrate to such distant 

 objects, when the brightness of them is not more than that 

 of these satellites. It is also evident, that the failure in these 

 latter instruments, arises not from want of magnifying power ; 

 as either of them has much more than sufficient for the purpose. 



Nov. 5, 1791. I viewed Saturn with the 20 and 40-feet 

 telescopes. 



" 20-feet. The 5th satellite of Saturn is very small. The 1st, 

 " 2d, 3d, 4th, 5th, and the new 6th satellite, are in their cal- 

 " culated places." 



" 40-feet. I see the new 6th satellite much better with this 

 " instrument than with the 20-feet. The 5th is also much larger 

 " here than in the 20-feet; in which it was nearly the same size 

 " as a small fixed star, but here it is considerably larger than 

 " that star." 



Here the superior penetrating power of the 40-feet telescope 

 shewed itself on the 6th satellite of Saturn, which is a very faint 

 object ; as it had also a considerable advantage in magnifying 

 power, the disk of the 5th satellite appeared larger than in the 

 20-feet. But the small star, which may be said to be beyond 



