XXX PBOOEEDINGS OE THE 



of the Observatory, a post which he continued to occupy to the 

 end of his life. 



This position gave full scope to his mathematical and inventive 

 powers, which were devoted, as it would seem, mainly to the im- 

 provement of optical instruments, and chiefly of those employed in 

 astronomical observations. His labours in this direction were 

 eminently successful. Amongst other inventions of the kind, it 

 may be mentioned that he contrived a micrometer of new con- 

 struction, by means of which he was enabled to measure the polar 

 and equatorial diameters of the sun. Professor Amici, though 

 holding a very high position among the astronomical observers of 

 the period, owes his reputation, perhaps, in greater measure to 

 the excellent instruments he either invented or improved, than 

 to the actual observations made by them. At the beginning of 

 the present centiiry he had constructed telescopes of large size, 

 with reflectors having an elliptical curve, by which the efiect of 

 spherical aberration is so much diminished. But the instrument 

 above all others that has rendered Amici's name famous is the 



MICROSCOPE. 



Though sometimes described as the original inventor of the 

 achromatic microscope, Amici cannot justly be so regarded, nor, 

 in fact, would it appear that any single individual is, strictly 

 speaking, entitled to that honour. Like many other important 

 inventions tending to supply a general want, the contrivance of 

 the achromatic microscope, as we now have it, seems to have been 

 almost simultaneously the result of the independent labours of 

 several minds. It is one of those inventions, if they may be so 

 termed, that form the culminating point of various attempts in 

 the same direction, when once the possibility of a successful 

 result has become apparent, and the desire for its accomplish- 

 ment generally and urgently felt. The following passage from 

 Dr. Carpenter's excellent work on the microscope will give a 

 correct idea of the part which is to be assigned to Amici in the 

 construction of the modern achromatic microscope : — " The first 

 successful attempt was made in the year 1823, by MM. Selligues 

 and Chevalier, of Paris, — the plan they adopted being that of a 

 combination of two or more pairs of lenses, each pair consisting 

 of a double convex of crown glass and a plano-concave of flint. 

 In the next year Mr. Tulley of London, without any knowledge 

 of what had been accomplished in Paris, applied himself to the 

 construction of achromatic object-glasses, and succeeded in pro- 

 ducing a single combination of three lenses, the corrections of which 



