REFRACTORS ACHROMATIC 1 09 



ciple on a large scale. Apparently the way here also 

 was barred against progress. All attempts to manu- 

 facture discs of pure flint glass larger than seven inches 

 in diameter failed. Up to that point the achromatic 

 refracting telescope was a great success. For seventy 

 years good specimens of considerable size were exceed- 

 ingly rare, and even in 1830 a disc of eleven inches and 

 seven-tenths in diameter cost flOOO. 1 An obscure 

 musician, considering it probably impracticable to ex- 

 tend the range of Dollond's telescope, or impressed by 

 the name and authority of Newton, was amusing him- 

 self, in 1772, if hard and continuous work can be called 

 amusement, with casting and grinding mirrors, with 

 mounting telescopes, and with studying the heavens in 

 Bath, the gayest and idlest city in England. The 

 people who formed the Literary Society of the town, 

 who met to read papers on scientific subjects, and some 

 of whom were members of the Royal Society of London, 

 did not even know him. They were pigmies ; a giant 

 was among them, of whose existence and works they 

 were not aware. 



The courage of this musician was extraordinary. In 

 the very year in which he removed to Bath, Messier, 

 an eminent French astronomer, warned the Royal 

 Society of London that progress in astronomy could 

 be hoped for only from refractors. His words are : 

 " It were to be wished that astronomers might be 

 accommodated with achromatic telescopes of the most 

 perfect construction, as such are the only instruments 

 whereby a great knowledge of the celestial bodies can 



1 Herschel sometimes used a 3^-feet achromatic or refracting tele- 

 scope and a single eye-lens to confirm apparently the evidence of his 

 20-feet or 7-feet reflectors. 



