375 



obj-.ective fronts than anything else. The President said they 

 hadl also another microscope, made by HeiT Leitz, and sent for 

 exh^ibition by Mr. Curties ; a foreign microscope without the 

 hor.'seshoe foot ! Truly a marvellous change. They had been 

 continuously told for so many years that the Continental model 

 was the only correct one ; the German instrument before them 

 embodied almost every English feature. With regard to the 

 Obej;haeuser model it had been all along in a state of continual 

 shift, until now in this the latest development of it, they had a 

 tripod scand, an inclining^ body, a rack-work coarse adjustment, 

 draw tube, an extremely ingenious fine adjustment, a rotating 

 nose piece, all of which were borrowed from English models. 

 In this instrument there was an Abbe condenser, with a mirror 

 fastened to the condenser. This plan of fixing the mirror 

 might be unobjectionable for daylight illumination, but with 

 artificial light the image of the source of the illumination 

 would be moved by every alteration in the focus of the con- 

 denser. There was also a turn-out arm with Abbe's rack-work 

 traversing diaphragm holder, which was of no use and much in 

 the Avay. The microscope was also fitted with a 13-leaved 

 diaphragm, very beautifully made, and a centring substage, 

 which was, however, applied to the condenser but not to the 

 diaphragm. But one of the most novel fittings in this micro- 

 scope was the way in which the groove for the substage was 

 contrived. It was not a Y, and the rack was not placed inside 

 it, and the problem at first sight was — how did they get a 

 smooth and proper fitting without grooves ? On examination it 

 was found to be done by means of a piece of steel with a spring 

 which was tightened up by screws at the back. He did not 

 know what was the price of this instrument complete, but he 

 was told it was the same as the old one. 



Mr. T. F. Smith thought that it would be a great improve- 

 ment if the iris diaphragm could be fitted so as to show on a 

 scale exactly what aperture was in use at any given position of 

 the lever. 



The President said Mr. Smith was quite right as to the 

 desirability of some means of ascertaining the aperture in use 

 at any position of the lever, but it seemed at present a difiicult 

 matter to accomplish because a very sraall movement of the 

 lever made a great difference in the size. 



