PROCEEDINGS OF THE SOCIETY. 283 



was indicated. His photographs of the Bacillus proteus vulgaris showed 

 clearly that the tangle of flagella at a certain point was not resolved till 

 this magnification had been reached. He had expressly stated, before 

 showing the photographs at 1S000 and 24,000 diameters, that they were 

 of no use as photographs. He quite agreed that they showed nothing 

 that the lower magnification did not show. He would go further and 

 say that they certainly did not show so much. But these photographs 

 had been taken from an entirely different point of view. In his opinion, 

 the most practical test that could be applied to an objective was photo- 

 micrography at extremely high magnifications. The indifferent objective 

 would break down under this test altogether. According to the degree 

 of success obtained the objectives could be appraised in regard to their 

 accuracy. From this point of view, the testing of the objective, he 

 considered photography at high magnifications of great value. He 

 could not accept Dr. Spitta's suggestion in regard to enlargement. That, 

 in his opinion, was not photomicrography. 



The President said he desired to add his congratulations to those of 

 Dr. Spitta and Mr. Scales to Dr. Vincent for his valuable paper. Knowing, 

 as he did, the other side of the .work for which the specimens were made, 

 he could say that the beautiful preparations shown to them formed the 

 least important part of Dr. Vincent's work. He returned him a most 

 hearty vote of thanks for his excellent paper, which was carried with 

 acclamation. 



Mr. F. W. Watson Baker read a paper on " Anomalies in Objective 

 Screw Threads." 



Mr. Shillington Scales said they were greatly indebted to Mr. Watson 

 Baker for his paper. The Microscopical Society not infrequently had 

 been blamed in connexion with its gauges, he thought in the main 

 undeservedly, and at the present time certain points dealt with by 

 Mr. Watson Baker were under discussion. But Mr. Baker had shown 

 how exceedingly erratic various makes of objective screw-threads were, 

 and his paper would prove a most valuable object-lesson to those workers 

 who, in using various makes of objectives, found themselves held up by 

 a screw thread which would not fit the Microscope. Mr. Baker's 

 suggestions deserved most careful consideration. 



The President thanked Mr. Baker, in the name of the Society, for 

 his paper, and hoped that some practical use would be made of his 

 valuable suggestions. 



The thanks of the Society were accorded to Mr. Baker for his paper. 



Mr. Shillington Scales read a paper by Mr. E. M. Nelson on " An 

 Objective Mount with an Iris." 



Mr. Shillington Scales said that it was difficult to take in all the 

 subject matter of a paper read rapidly, but he would like to call atten- 

 tion to two points which had struck him. Mr. Nelson had apparently 

 suggested the measuring of objects by shutting down the numerical 

 aperture until the object became invisible. To him this seemed a 

 startling proposition. Though an objective of a given aperture was 

 theoretically capable of dividing a certain number of lines, this was not 

 the same thing as seeing more widely separated objects of minute size. 



