154 



IX. — Gregory and Wright'* Microscope. 

 By Edward M. Nelson. 



(Read December 18, 1907.) 



An old and rare book has just turned up which bears upon the 

 evolution of the Microscope at an important period of its history, 

 viz. when it was just beginning to crystallise into its present form. 

 If you will refer to this Journal for 1899, p. 325, a description will 

 be found of an interesting Microscope presented by Dr. Dallinger. 

 This Microscope, not signed, was thought to be of Benjamin Martin's 

 workmanship; now, however, it is possible to read its history more 

 accurately. 



The book from which this new information is derived, pub- 

 lished in 1786 by Messrs. Gregory and Wright, opticians, No. 148 

 Leadenhall Street, describes a " New Universal Microscope, 

 which has all the uses of the Single, Compound, Opaque, and 

 Aquatic Microscopes." The plate in the book from which fig. 32 

 is copied shows that this Microscope is almost identical with 

 that in the Society's cabinet. It has the same folding tripod- 

 foot with the compass joint at the bottom of the limb, it has 

 the same shaped body with a coned end, and the movement of the 

 body, backwards and forwards and also in arc, is the same, even 

 to details of ornament. There is the same holder for either the 

 substage condenser or for the lieberkiihn, and the same Benjamin 

 Martin pivoted super-stage. The difference between the instru- 

 ments is that Gregory's is a stage, and the other a body focuser. 

 It is evident that in Gregory's Microscope we see a Benjamin 

 Martin's latest type of instrument — in brief, a small edition, 

 without accessories, of the magnificent instrument he made for 

 George III., which is in the Society's cabinet. The limb, which is 

 pivoted by a compass joint to the top of the tripod foot, is an equi- 

 lateral prism ;* the rack is cut into the base of this prism at the 

 back, and the pinion, which protrudes at right angles from the base 

 of this triangle, moves up and down with the stage. If we now 

 examine the limb of the Microscope presented by Dr. Dallinger, 

 we shall find that it is a tube of circular section, with an inner 

 tube actuated by rack-and-pinion, and a third, a push-tube, inside 

 this one to hold the body. The push-tube is the coarse-adjustment, 

 and the rack-and-pinion the fine-adjustment. It is evident, there- 

 fore, that Dr. Dallinger' s is a later and improved form of 



* See this Journal, 1903, p. 589, fig. 144. 



