PROCEEDINGS OF THE SOCIETY. 321 



tures merely by tlie optical images produced by them, was entirely 

 illusive. If Mr. Smith based bis conclusions on such grounds, then be 

 could only say tbat bis explanations were quite beside the mark, a,nd, 

 unless be would intelligently follow up tbe Abbe diffraction theory and 

 make himself master of tbe practical conclusions to which it pointed, 

 bis remarks upon the subject could possess no value whatever. 



Mr. Smith said be had brought these photographs for exhibition 

 rather as test objects, than as showing the structure. 



Tbe President said they were very glad to have seen the photographs, 

 many of which were extremely interesting ; but as regarded the nature 

 of the structures that Mr. Smith thought he could determine, he rather 

 agreed with what bad been said, that under tbe conditions it was at 

 present a somewhat hopeless matter. 



Mr. E. M. Nelson's letter was read as follows : — 



" Some time ago I had the honour of bringing to the notice of the 

 Eoyal Microscopical Society tbe different appearances a transparent posi- 

 tive of an AmpJiipleura pellucida presented when viewed under different 

 sources of illumination. I now find that a film of water on the surface 

 of the gelatin will cause an alteration in the image similar to that made 

 by tbe edge of tbe flame in the former case. When the film of water 

 has run off tbe gelatin the image is normal, although the gelatin is 

 saturated with water. Tbe saturation of tbe gelatin with water has 

 nothing whatever to do with it; what is necessary to produce tbe 

 phenomenon is that a film of water should be on the surface of the 

 gelatin. I consider this matter extremely important, as I know of no 

 physical law of light which will account for these strange appearances. 



I also inclose a photomicrograph of the ' filament ' at tbe head of a 

 human spermatozoon. It is a very delicate object, and can only be seen 

 in tbe Microscope with close attention." 



Mr. J. Mayall, jun., said tbat at tbe Stuart Exhibition, now open at 

 tbe New Gallery in Eegent Street, there was a Microscope said to have 

 belonged to Charles I. At Mr. Crisp's request he went to examine it, 

 but, on viewing the Microscope, he found that it had been misnamed. 

 He held in his band a Microscope from Mr. Crisp's museum, which was 

 identical with the so-called Charles I. Microscope, except tbat it pos- 

 sessed a clamping collar : in fact, when he that day put the two 

 instruments side by side they were found to be so exactly alike that 

 they could only be distinguished by the covering of the tubes, which 

 in one case was of parchment, and in the other of red leather. Having 

 established the identity of the two forms, the question arose as to when 

 they were made, and he thought this was conclusively settled by reference 

 to an old work in Mr. Crisp's library, which contained a figure of tbe 

 instrument, and assigned the date as 1686. In M. Nachet's collection 

 there was also a model, which almost exactly corresponded with it. The 

 body-tube was a good specimen of Italian work of the 17th century, and 

 in tbat case it bad been traced to the possession of Homberg, a member 

 of the Academy of Sciences of Paris. The same kind of work was also 

 seen in a model which belonged to Pope Benedict, also in one at the 

 Jena University, and in one belonging to George III. One peculiarity 

 1889. z 



