182 PROCEEDINGS OF THE SOCIETY. 



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Mr. J. May all, jun., at the request of the President, directed the 

 attention of the meeting to eleven photomicrographs which had been sent by 

 Dr. ^'an Hcurck, and which the latter thought showed results of exceptional 

 merit. The one of Ampldpleura peUucida by transmitted light was rather 

 striking ; it showed apparently two series of lines which were resolved into 

 dots, and, so far as he was aware, this was the best of the kind he had yet 

 seen. But Dr. Yan Heurck did not say whether it was taken from a specimen 

 taken from a dense medium or not, nor what was the actual magnification 

 employed. In the pamphlet which accompanied the photographs it was 

 stated that " no diffraction lines were visible whatever," but on examina- 

 tion, unless he was much mistaken, they had been painted out on the 

 negative, so that Dr. Eoyston-Pigott, in his remarks uj)on this supposed 

 fact, had made what the French called a boidetle. If it was desired to give 

 such photogi'aphs a real value the background should not be interfered 

 Avith, and a small tablet should be left on which should be written the 

 particulars as to magnification, moimtiug, and other data which it was 

 essential to be in possession of in order to form any reliable opinion. In 

 the case of P. angulatumhG thought the photograph rather failed to show the 

 results satisfactorily. It would have been better if only a small portion of 

 the valve had been shown including the fracture. As regarded the longi- 

 tudinal lines of Ariiphipleura pellucida, he had submitted them to Prof. Abbe, 

 who said that as they appeared closer than the diffraction lines, that was 

 a satisfactory demonstration of their existence in the object. As to the 

 photograph of P. angulatum, in which a central spot was shown, all who 

 were familiar with the object were aware that they could get the appearance 

 of a central spot or not, according to how they looked at it. It was a 

 question of change of focus. SiirireUa gemma he thought was not better 

 shown than in Dr. Woodward's photogi'aphs. Then there were j^hotographs 

 of Nobert's lines, which were said to be those of the 18th and 19th bands ; 

 but here again there was nothing to enable one to identify them, or to s.iy 

 they were not the 14th and 1 5th bands. 



The President, iu thanking Mr. Mayall for his remarks, said it must 

 be obvious to all that it would be of immense advantage to have the data 

 by which alone they could form anything like a correct judgment as to the 

 value of these, or indeed any other specimens of photomicrography. He 

 thought also that it would be of advantage if they could have the oppor- 

 tunity of comparing these with those of Dr. Woodward. 



Mr. J. Beck said he had not looked at any of the jihotographs except 

 that of AmjjMpJeura, but he should say that the manipulation which it had 

 gone through had entirely destroyed its value. 



Dr. Millar called attention to a photomicrograi)h of P. an/julatum taken 

 by M. Nachet in 1867, which was fully as good as the one now shown. 



The President stated that it was proposed by the Council to fill up the 

 vacancy in their list of Honorary Fellows by electing Mr. P. H. Gosse, F.R.S. 



Mr. M. Pillischer exhibited his new " Kosmos"' Microscope, which was 

 described by Mr. J. Mayall, jun., as being made on the Continental model, 

 with a short body and a direct-acting screw, the screws being bevelled off 

 and the corners rounded. There was a very symmetrical foot, and the 

 finish given to the instrument made it very nice to touch. The mirror 

 was made with a neat swinging motion, and was of a somewhat shorter 



