48 , EYE. 



colors come to a point at different distances, and thus 

 create several circles, which makes a confusion. 

 This was long found to make our telescopes imper- 

 fect, insomuch that it became necessary to make them 

 of reflectors or mirrors, and not of magnifying glas- 

 ses." But it has since been discovered, that if cer- 

 tain different kinds of glass, viz. flint glass and crown 

 glass, be placed together, so as to make a compound 

 magnifier, they serve to correct this defect. No rain- 

 bow is then produced. The improvement was intro- 

 duced not many years ago, in the celebrated teles- 

 copes known by the name of the Dolland telescopes. 

 But it is now ascertained, that the whole discovery 

 was well understood in the first telescope that ever 

 was constructed ; that is, in the eye. " It is found 

 that the different natural magnifiers of the eye are 

 combined upon a principle of the same kind." What 

 is more curious, thirty years after the time of Dolland, 

 a discovery was made by Dr. Blair, of Edinburgh, of 

 the greatly superior effect which combinations of fluid 

 and solid magnifiers have in correcting the imperfec- 

 tion ; and, most wonderful to think, when the eye is 

 examined, we find it contains solid and fluid magni- 

 fiers combined, acting naturally upon the same prin- 

 ciple which was thus recently found out by many in- 

 genious mechanical and chemical experiments. 



B. One can hardly understand so much contri- 

 vance ; and yet it is beautiful as an evidence of de- 

 sign, and of an all- vise Author, to find so much ma- 

 chinery in the eye, which shews the deepest acquaint- 

 ance with philosophical principles ; and to know that 



