j"i%ST?m] ^oycd Microscopical Society. 127 



cathedra. The Society also will learn with regret that Mr. Wenham 

 is now unable to take his place amongst us and to add, as heretofore, 

 to the interest of our discussions. 



Among the many valuable presents received during the past year, 

 the Amici reflecting microscope, presented by Dr. Millar, requires 

 a special notice. As Holland's Triplet was the culminating point 

 of the single microscope, so the Amici Bejlector was a stand-point 

 in the history of the compound microscope. It is not too much 

 to say that the compound microscope had been in what we may 

 term an embryo state for a period of nearly 200 years. Griendelius 

 in 1687 published in his work on the Microscope a diagram and an 

 account of a compound microscope, the compound positive eye-piece 

 consisting of two pairs of plano-convex lenses placed with the 

 convex surfaces towards each other, an arrangement superior per- 

 haps to Eamsden's, and, what is very remarkable, the object-glass of 

 that early microscope is compound also, consisting of two plano- 

 convex lenses of short focal length, as in Wollaston's celebrated 

 doublet, the convex surfaces being hyperbolic curves. Spherical 

 aberration, however, would necessarily confine such a construction 

 within the limit of low powers, and the achromatic objective had 

 not yet become a matter even of mathematical speculation. Errors 

 from curvature and colour seemed for a long time to be looked upon 

 b}' opticians as a sine qua non, and to be accepted as an inherent 

 and ii-removable blot upon their work. Nor did mathematicians get 

 them out of the scrape until Amici, in our own day, threw the 

 refracting medium overboard, and, after the example of Newton, used 

 a small speculum for high and low powers. In the exterior of the 

 Amician microscope there is indeed a prima facie resemblance to 

 a Newtonian telescope ; but, as Dr. Goring justly remarks, " the 

 form of the concave metal and the situation of the radiant point are 

 so totally different as to constitute a new instrument." 



The instrument presented to the Society by Dr. Millar was made 

 by Cuthbert. Dr. Goring gives a very minute description of it in 

 his ' MiCEOGRAPHiA,' Speaking of Cuthbert and himself as " the 

 parents of the instrument i}i its effective form." I was fortunately 

 able to complete Dr. Millar's instrument by adding to it the deeper 

 objective metals, and these, in Dr. Goring's opinion, became in- 

 valuable when Cuthbert's loss of sight stopped his work. Yet, 

 under my own eyes, this good old man when blind, but owning an 

 inner hght, figured to perfection a small speculum for my Gregorian 

 telescope, saying with the blind old poet, " Yet not the more bate I 

 one jot of hope, but hold right on." 



As the triplet gave place to the more aplanatic speculum, so 

 the latter was ultimately superseded by the Achromatic objective. 

 Wm. Tulley was the first among English opticians to produce a 

 single uicemented achromatic triple, xoths of an inch in focal 



