318 EDWARD M, NELSON ON AN IMPROVED 



Frant^'ois Watkiiis* ; (2) the mirror is for the first time attached 

 to the limb and not eitlier to the box or to the foot ; (3) the 

 distance of the mirror from the stage can be varied, as there 

 are two holes, one above the other about one inch apart, in the 

 limb ; and the mirror, to which a pin is fitted, can be attached 

 to either of them. 



The above improvements, of which these are the first examples, 

 have remained to the present time. The limb is attached to the 

 top of the box foot by a dovetail slide ; when the microscope is 

 packed in its box a plain plate of l)rass is placed in its stead to 

 preserve the dovetail. 



The bull's-eye is attached to the right-hand side of the stage 

 instead of the front as in Cuff's. 



The figure in the pamphlet is a copy of Cuff's, for the ribbon on 

 the fish-pan is wound in the same way and there are the same 

 reflections in the various glasses ; the microscope itself, with the 

 exception of the details mentioned above, even in its ornamenta- 

 tion, is precisely similar to Cuff's. 



There has always been a difiiculty in dating microscopes of 

 this period owing to the uncertainty of the date of Cuflfs death 

 or retirement from business. Here we Iiave an authentic and 

 dated copy of one of Caff's microscopes in 1751. It is not 

 conceivable that such a flagrant plagiarism would have been 

 perpetrated. We know from Adams's illustrated catalcf^ue that 

 he was making all Cuff's models in 1771. We also have in 

 Ellis's work on the Corallines (1755) a description of the aquatic 

 microscope Cuff made for him. So it has been customary to fix 

 the date of Cuff's retirement from business between the years 

 1755 and 1771. But obviously the publication of Ellis's work in 

 1755 does not imply that his microscope was made in that year ; 

 * Jowni. 11. M. Soe., 190, p. ]43, lig. 26. 



