276 HERSCHEL. 



Practical astronomers know how much the mounting 

 of a telescope contributes to produce correct observations. 

 The difficulty of a solid yet very movable mounting, in- 

 creases rapidly with the dimensions and weight of an 

 instrument. We may then conceive that Herschel had 

 to surmount many obstacles, to mount a telescope suit- 

 ably, of which the mirror alone weighed upwards of 

 1000 kilogrammes (a ton). But he solved this problem 

 to his entire satisfaction by the aid of a combination of 

 spars, of pulleys, and of ropes, of all which a correct 

 idea may be formed by referring to the woodcut we have 

 given in our Treatise on Popular Astronomy (vol. i.). 

 This great apparatus, and the entirely different stands 

 that Herschel imagined for telescopes of smaller dimen- 

 sions, assign to that illustrious observer a distinguished 

 place amongst the most ingenious mechanics of our age. 



J/ ^3 <^J CJ 



Persons in general, I may even say the greater part 

 of astronomers, know not what was the effect that the 

 great forty-foot telescope had in the labours and discov- 

 eries of Hersch'el. Still, we are not less mistaken when 

 we fancy that the observer of Slough always used this 

 telescope, than in maintaining with Baron von Zach (see 

 Monatliche Correspondenz, January, 1802), that the co- 

 lossal instrument was of no use at all, that it did not con- 

 tribute to any one discovery, that it must be considered 

 as a mere object of curiosity. These assertions are dis- 

 tinctly contradicted by Herschel's own words. In the 

 volume of Philosophical Transactions for the year 1795 

 (p. 350), I read for example: "On the 28th of August 

 1789, having directed my telescope (of forty feet) to the 

 heavens, I discovered the sixth satellite of Saturn, and I 

 perceived the spots on that planet, better than I had been 

 able to do before." (See also, relative to this sixth satel- 



