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better of histological subjects. One of Spermatic tubes, and 

 another of Kidney were well worth special notice. To produce 

 good — that was useful — photographs of anatomical structure it 

 was, of course, necessary to select good preparations in which 

 the details wanted were really well shown. This could, as a 

 rule, only be done by persons who understood what the 

 structure was, because these things were not like diatoms — all 

 alike — except as to clean or unbroken condition. 



Mr. C. Haughton Gill thought Mr. Smith had rather mis- 

 understood his remarks, from the quotations made in his paper 

 as to the use of the light filter, because if he really said that 

 owing to its use he could with a cheap ordinary achromatic 

 make as good photographs as could be obtained by expensive 

 apochromatic objectives, that was not the meaning he had 

 intended to convey. What he meant was that because a person 

 did not possess these expensive lenses he need not give up the 

 idea of making good photographs, since by the use of the light 

 filter they could photograph anything, which the lens they had 

 would show ; but, of course, things which were beyond the 

 resolving power of a lens could no more be photographed than 

 they could be seen by it. Given the use of the light filter, 

 they could photograph all they could see. Two very good 

 lenses which he had used were one of Beck's ordinary yoin., 

 and one of Reichert's 35s. objectives, which he found to be a 

 very good achromatic of its kind. He did not quite follow Mr. 

 Smith's remarks as to the iso-chromatic plates bringing the 

 chemical and visual foci together again after they had been 

 separated by the lens. That he got a sharp image in the focus 

 of the visual rays there could be no doubt, but the reason of this 

 was that these plates were sensitive to the rays, which were 

 active in producing the visual focus, and, therefore, it was not 

 necessary to work with a focus nearer the violet end of the 

 spectrum. The plate did not cause the two foci to become 

 coincident, but only enabled a sharp picture to be taken by the 

 visual rays. 



Mr. Smith said he was not at the meeting when Mr. Gill read 

 his paper, but had taken his idea from a report which he saw 

 in the " English Mechanic." 



The Chairman thought they ought to be extremely thankful 

 that this cheap series of objectives was being added to and 



