Gregory and Wright's Microscope. By E. M. Nelson. 1 57 



It has been said that the modern Microscope was evolved from 

 Straus Durckheim's drum Microscope, made by Oberhaeuser in 

 1835, but between that and the hinged limb Microscope of the 

 present day there is nothing in common, and no continuity. 



Before closing, allow me to correct a mis-statement in a former 

 paper (see this Journal, 1901, p. 729), where in a description of a 

 Powell Microscope of 1840, presented to the Society by Messrs. 

 Watson, I stated, upon the authority of Hannover,* that Fraunhofer 

 was the designer of the screw-stage micrometer. A similar state- 

 ment is made in the 9th ed. Ency. Brit., art. Fraunhofer. The 

 screw-stage micrometer and webbed eye-piece are described by 

 Benjamin Martin in his Optical Essays (1770),f page 48, and 

 were fitted to his large instrument in our cabinet. Fraunhofer 

 was not born until five years after Martin's death. 



A correction is also needed in a paper on the rackwork coarse- 

 adjustment (see this Journal, 1899, p. 262, Synopsis), where I 

 stated that the Microscope " Body-focuser," one inch of rack in 

 slot in tube (telescope form) ; example in Society's cabinet," was 

 made by Benjamin Martin, circa 1776 ; for this, read made by 

 Gregory and Wright, circa 1795. 



* English Translation, 1853, p. 67, pi. 1, fig. 12. 



t Martin's Optical Essays are not dated, but we learn from Adams on the 

 Microscope, 1798, p. 21, that they were published in 1770. 



