Gregory and Wright 1 s Microscope. By E. M. Nelson. 155 



Gregory's. Now we know from the book that the date of 

 Gregory's is 1786, and therefore we can say with certainty 

 that Dr. Dallinger's was not made by Benjamin Martin, as he 

 died in 1782. It is more than probable that Gregory and Wright 

 became Benjamin Martin's successors, and were the makers of the 

 Microscope presented by Dr. Dallinger. It is interesting to 

 notice the name of Gregory's Microscope " Single, Compound, 

 Opaque, and Aquatic." In early days Microscopes were termed 

 " single " and " double," because they consisted of one or two 



Fig. 32. 



lenses, but after the " body lens " (field glass) was added by 

 Monconys, in 1660, the word " double" became inappropriate, and 

 it appears that " compound " was substituted for it by Dr. Smith 

 in 1738 (Compleat System of Optics) ; in this he was followed 

 by Benjamin Martin (Optical Essays), 1770. " Double " was 

 last used by Wood (Master of St. John's College, Cambridge), in 

 his Optics, 1818, but "single" lasted for nearly a century longer, 

 until it was displaced by Wollaston's invention of the doublet in 

 1829, and so, in 1830, we find the word " simple " in Coddington 



m 2 



