PEOCEEDINGS OF THE SOCIETY. 155 



Mr. James Smith said that, in working with high powers under 

 the binocular, he had always found it of great advantage to use a 

 finely-ground glass slip under the slide on which the object was 

 mounted. If a l-4th in. or a l-8th in. were used under ordinary cir- 

 cumstances, the black division across the field was seen, but the 

 ground glass seemed to obliterate this entirely. He generally used a 

 piece of very pale blue glass, ground on the upper surface. 



Mr. Stewart referred to the importance of approximating the back 

 lens of the objective to the binocular prism. With the ordinary 

 Wenham prism they were limited to powers of 400 to 500, but with 

 the Stephenson arrangement it was quite easy to work with a l-25th in. 

 There seemed still to be persons who appeared to think that the 

 binocular was a mere toy. It was, however, of really great import- 

 ance, especially when working on an exceedingly transparent object, 

 where the inner membranes could be seen distinctly separated from 

 those above them ; or in tracing out fine nerve-fibres, which, passing 

 over or under each other, could be resolved in a way which was 

 entirely impossible by any other means. 



Mr. Crisp pointed out the means that had been adopted for using 

 the Wenham prism with the higher powers by fitting it into a tube 

 which could be passed inside the objective. 



Mr. Beck believed they were only as yet in the infancy of the 

 binocular Microscope, and he looked forward to the time when much 

 more attention would be paid to its construction, and particularly to 

 the question of ascertaining the best point at which the prism should 

 be placed to get the full field without adventitious aid in the way of 

 illuminators, by which improved results would no doubt be obtained. 

 He believed that the binocular was the Microscope which would be 

 used in the future. 



Dr. Wallich said that with reference to ground glass he might 

 mention that some time ago he accidentally found some glass which 

 had been near a guttapercha bottle of hydro-fluoric acid, the fumes of 

 which had acted upon the glass and frosted it in a far finer manner 

 than could be done with the finest emery powder. The condenser he 

 used was the ordinary " Gillet," with which he had no difficulty. 

 Another thing which he found very useful with the bull's-eye con- 

 denser was to fix a piece of light-blue glass on the near side of it ; the 

 light from this was so good that he could confidently recommend the 

 plan. 



Dr. Gibbes said he could corroborate all that had been said on the 

 subject of the binocular, and especially its value when used with a 

 1-12 in. in examining those very minute parasites to which his atten- 

 tion had been given, as it enabled him at once to see whether they 

 were outside or inside the tissue. 



Mr. Dreyfus's Note was read, describing a safe method of packing 

 slides in a cabinet for railway and sea transit (see p. 146). 



