PROCEEDINGS OF THE SOCIETY. 269 



MEETING 



Held on the 21st of March, 1900, at 20 Hanover Square, W., 

 A. D. Michael, Esq., F.L.S., Vice-President, in the Chair. 



The Minutes of the Meeting of 21st February last were read and 

 confirmed, and were signed by the Chairman. 



The List of Donations to the Society since the last meeting (exclu- 

 sive of exchanges and reprints) was read, and the thanks of the Society 



were voted to the donors. 



From 



Marion J. Nowbigin, Colour in Nature. (Svo. London, 1898) The Publisher. 



An old Microscope by Benjamin Martin Mr. F. B. Dixon-Nuttall. 



With reference to the Microscope presented by Mr. Dixon-Nuttall, 

 Mr. B. M. Nelson said this was a Microscope made by Benjamin 

 Martin, dating about the year 1765. It was particularly interesting to 

 the Society because they had not one of this form in their collection. 

 A solar projecting apparatus was packed in the same box ; this was the 

 invention of Dr. Lieberkiihu, who brought it to London in 1740; Curt' 

 improved it by adding the mirror in 1743. It was a very well made 

 and perfect example. 



Mr. E. M. Nelson called attention to a number of Microscopes 

 which had been sent to the Society for exhibition that evening. 



The first of these was by Plossl, kindly sent by Mr. C. L. dirties. 

 Mr. Parsons has found that this Microscope had already been illustrated 

 in our Journal for 1883, p. 703 ; but as it was now probably forgotten, 

 he would ask the Fellows to inspect the very peculiar coarse adjustment 

 that was fitted to the instrument. The principle, was similar to that of 

 the reciprocating movement of a steam-engine. The body-tube was the 

 piston-rod, and the head of the coarse-adjustment pinion, which was 

 large in diameter, was the fly-wheel. A pin placed near the periphery 

 of this wheel was connected to the body-tube by a connecting-rod ; 

 therefore on turning the wheel reciprocating movement was imparted 

 to the body-tube, and this formed the coarse adjustment. 



The next five Microscopes had kindly been sent by Messrs. Spiers 

 and Pond. The first was an English model similar to the ordinary 

 pattern of Student's Microscope. 



The next was a French model, with a plain sliding tube coarse 

 adjustment, and a short lever nose-piece fine adjustment. This latter 

 worked in a slot cut in the outer tube; in order therefore to effect the 

 coarse adjustment, it was necessary to move the tube directly up or 

 down ; a gradual adjustment by turning the tube round was impossible. 



The next was a smaller instrument fitted with a coarse adjustment 

 of a very peculiar kind ; it was evidently a modification of Plossl's, but 

 the connecting arms were suppressed, and a pin working in a radial 

 slot in the willed head of the coarse adjustment was substituted for them. 



