780 PROCEEDINGS OF THE SOCIETY. 



Mr. J. W. Gordon exhibited some remarkably fine plioto-micrograplis 

 •of Pleurosigma Angulatum, taken with a compounding draw tube fitted 

 with a vibrating screen, such as he had recently exhibited at a Meeting 

 of the Society, and described at p. 420 of his paper published in the 

 August Journal. The instrument employed in producing them was 

 fitted with a -j^-in. oil immersion as the principal objective, above which 

 a sj-in. objective was mounted to act as a magnifier ; and the photo- 

 graph then obtained was further enlarged by the usual camera process. 

 The whole magnification obtained was 396 X 24 = 8500 : 1. The 

 source of illumination in this instance was a pin-hole lighted by a 

 Welsbach burner. He thought it would be better to use a limelight for 

 the purpose, because with a Welsbach mantle the stitches of the fabric 

 were discernible in the field of the instrument ; and, although they were 

 sufficiently large and out of focus not to destroy the details, the some- 

 what striped effect altered the appearance of the picture as a photograph. 

 (Unfortunately, through some temporary disarrangement of the Epidia- 

 scope, an; attempt to show the photographs upon the screen was not 

 sufficiently successful to afford any idea of the sharpness of detail so 

 remarkable in the prints, which were therefore handed round for 

 inspection.) 



Mr. C. Beck regretted that the photograph did not show to full 

 advantage on the screen, but the original would be found much better ; 

 it was of special interest on account of the means by which it had been 

 produced. When it was considered that it had been taken through a 

 ground-glass screen, rapidly oscillated, it iwas astonishing that the hexa- 

 gonal markings were clearly shown. Another remarkable thing about it 

 was, that the original image formed by the Microscope had been magnified 

 by another Microscope to the extent of X 150, whereas the microscopic 

 image viewed with an A eye-piece is only magnified x 5. The result 

 certainly left no doubt that Mr. Gordon had demonstrated the perfect 

 success of his method, which some persons must have looked upon with 

 horror at the time when it was first mentioned. 



Mr. J. AV. Gordon said that Mr. Beck had referred to a ground- 

 glass screen. He had mentioned this in his former communication, and 

 most of his work had been done with such a screen, but he ought to 

 have said that the particular specimens before the Meeting were taken 

 with a screen formed of a thin film of wax between two cover glasses, 

 which, although not quite so diaphanous as ground glass, had some 

 advantages. He had used this because he had it by him at the time ; 

 although it was not better for photography than a ground glass it was 

 certainly better for the eye, as a scintillating effect was produced by 

 ground glass however finely it had been rubbed down. In the wax 

 film, on the contrary, the grain was so inconspicuous that when the screen 

 was set in vibration it wholly disappeared, and with this therefore they 

 got rid of the scintillation altogether. 



The thanks of the Society were cordially voted to Mr. Gordon for 

 his communication. 



Mr. F. W. Millett's paper " On the Recent Foraminifera of the Malay 

 Archipelago " — being part xv. of the series — which he had contributed 

 to the proceedings of the Society, was taken as read. 



