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improved every day. When tliey could get a lens for 20s. or 30s., 

 which, for many purposes, would rival the best apochromatics, 

 it was a very great advantage, and every month they seemed to 

 be getting more perfect lenses, in which the spectrum was 

 marvellously corrected. He could not speak offhand as to the 

 merits of the iso-chromatic plates, but the results shown that 

 evening were worth looking at. Mr. Grill had, no doubt, 

 perfectly explained their action, which could not be due to 

 their bringing the chemical and visible foci together, but was 

 due to the image-forming rays being the active rays, where 

 these plates were employed. As regarded the screen, it would, 

 of course, be more convenient if it could be made of solids 

 rather than liquids, and he had met with some success by 

 combining different tints of coloured gelatin obtained from 

 " Tom Smith's crackers" with coloured glass. The next thing 

 he hoped to do was to get a screen made all of glass. The 

 Germans had criticized a term which had come into use, he 

 thought, at his own suggestion — semi-apochromatic — they 

 objected to it on the ground that there could be no such thing ; 

 a glass must be either apocliromatic or achromatic, and could 

 not be half and half. When they took what was considered 

 to be a first-rate achromatic lens six years ago and compared it 

 with the best apochromatics there was an enormous difference 

 between them ; but there was if anything less difference be- 

 tween the new series and the apochromatics than there was 

 between the new series and the old achromatics, so that there 

 was ample justification for the new term. 



The thanks of the meeting were voted to Mr. Smith for his 

 paper. 



Mr. Karop said they had received a paper from Mr. T. B. 

 Rosseter, describing two new Cysticerci, of which well-drawn 

 figures were also sent in illustration. Mr. Rosseter had been 

 giving a good deal of attention lately to this subject, and it 

 would be very useful to have his observations put on record. 

 The time was, however, too far advanced to read it in extenso 

 that evening, but it would be taken as read, and would appear 

 in the Journal in usual course. 



The thanks of the Club were voted to Mr. Rosseter for his 

 communication. 



Announcements of meetings, etc., for the ensuing month 



