161 



ribbons, connective and barrel-shaped forms were all well shown. 

 Mr. Gilbert read a paper on this subject which appeared in the 

 1st volume of the Journal, 2nd series. 



The President exhibited a form of lens mirror, combining the 

 principles of the pocket lens and Lieberkuhn. In its simplest form 

 it was a plano-convex lens with the convex side silvered, and the 

 silvering removed from the centre to form an aperture through 

 which the object could be viewed — another lens of suitable form 

 being added to it — it was held up towards the light and became 

 its own illuminator by converging a strong beam upon the object. 

 He had just computed an achromatic form which he hoped to 

 show them at some future meeting. 



He thought the members of the Club who were interested in 

 optical matters would be glad to know of a new photographic 

 camera lens which had recently been brought out. Of late years 

 camera lenses had made enormous strides, chiefly owing to the 

 introduction of the Jena glass, by the use of which astigmatism 

 had been more perfectly corrected. The latest development came 

 from Munich ; this was a lens of 8J focus, fitted with an iris 

 diaphragm, and the price of the whole thing was 25s. It was about 

 the same as the cost of an English iris diaphragm, and they got 

 the lens thrown in. The novelty of the thing was that there were 

 no compound lenses in it, and so far as the photographic results 

 were concerned it was one of the sharpest lenses he ever saw. 

 In use the lens was first focussed in the usual way for the 

 visual rays, and then it was pushed back and turned into a slot 

 which gave them the exact focus of the actinic rays, and then 

 the picture was taken, which covered a ^ plate well. He brought 

 the matter before the Club because of the novelty in the con- 

 struction of this lens, and the question arose, could not this or 

 some similar plan be adapted to photo-micrographic lenses ? 



Mr. E. B. Green again exhibited a number of specimens and 

 drawings of his so-called parasitic growths on the root hairs 

 of plants. The thanks of the Club were voted to Mr. Green for 

 his beautiful exhibition. 



The Secretary said that since their last meeting the Journal had 

 been issued, and he hoped that every member had received his copy. 



Announcements of excursions and meetings for the ensuing 

 month were then made, and the meeting terminated with the 

 usual conversazione. 



