Dr Goring on Monochromatic Light, Sfc. 63 



the thing done effectually, if possible, by London artists, which 

 resolution I executed afterwards. In the course of these expe- 

 riments I found the utility of getting the power at the objec- 

 tive, instead of the ocular, end of the instrument, as a much 

 sharper image was thereby obtained. I accordingly deepened, 

 what I shall call the object-glasses, as far as one-fourth of an 

 inch focus, and obtained a very superior microscope; an account 

 of which has already been laid before the public. 



As to achromatism, however, I regret to state that the Lon- 

 don workmen sacceededno better than MrAdie, though I am not 

 quite certain if a feeble compensation was not produced some- 

 times, when the curves of the two plano-convex lenses, which 

 composed the object-glass, were turned towards each other in 

 the manner they have been engraved. I moreover once 

 thought that I had got a combination that was achromatic, at 

 least upon opaque objects ; and being determined to leave no- 

 thing to be done by any man who should take up the subject 

 after me, I resolved to apply to Mr Tulley of Islington, to 

 have his opinion and advice on the subject. He soon convin- 

 ced me of the impossibility of obtaining achromatism in any 

 case where an image xcas to be formed from a real object, 

 otherwise than by the action of concaves of flint-glass, and 

 that my ignorance of the art of seeing the flaws and imperfec- 

 tions of optical instruments was the sole cause of my suppos- 

 ing I had ever obtained even an approximation to achroma- 

 tism. 



Now, as my respect for tridy exact science is not surpassed 

 by that of any man, I must confess that all these circumstances 

 created in my mind some doubts and misgivings as to the ac- 

 curacy of Professor ltobison 1 s statements and theories, not very 

 much unlike what I have observed in farmers in the country, 

 when unable to reconcile the actual state of the weather with 

 the predictions of Moore's Almanack, in which their faith is 

 altogether inflexible. 



These theories of Professor Robison seem to have been re- 

 suscitated by Professor Airy and Mr Coddington. The work 

 of the latter gentleman on the refraction and reflection of light, 

 contains the substance of Professor Airy's papers on these sub- 

 jects; and whether it is considered as a work of originality, or 



