74 BELL. 



John Hadley in fact was the real inventor of the reflector in quite 

 the same sense that Mr. Edison invented the incandescent lamp; 

 from grasping the true principles of the matter and carrying them out 

 to success while the only previous attempts had ended in dismal 

 failure. 



It was Hadley who taught the art to Molyneux and others and to 

 whom James Short, the most celebrated of eighteenth century artists 

 until the time of Herschel, was undoubtedly indebted for the start 

 upon his brilliant career. 



Short, however, worked to the Gregorian principle with success, 

 doubtless since because this telescope rectifies the image, it is avail- 

 able both for terrestrial and celestial use. He made instruments from 

 all accounts of beautiful figure, some of them up to 8 or 10 inches diam- 

 eter, and of a speculum metal so nicely compounded and polished that 

 some of his specula were still serviceable well toward the end of the 

 nineteenth century. 



There is good reason to suspect that Short may have been the in- 

 ventor of the system of distributed grooves given to the tools, upon 

 which successful figuring so much depends, since, dying, he ordered 

 the destruction of his whole equipment, a quite needless precaution 

 against the success of posterity had there not been very radical im- 

 provements, easily detected. James Short, too, was the first con- 

 structor of genuine equatorial mountings of which he executed several 

 about the middle of the eighteenth century. He died leaving the 

 methods which led him to success a mystery unsolved, for Herschel 

 and his successors to puzzle over. The only change in the situation 

 after Herschel 's day was the independent invention of Steinheil and 

 Foucault which gave to silver-on-glass its present supremacy. The 

 earliest examples of Foucault's work show how little, otherwise than 

 in the material and figuring of the speculum, the art of telescope con- 

 struction had progressed since Hadley and Short were working a 

 century before. 



