410 PROCEEDINGS OF THE SOCIETY. 



Dr. Hebb said that in the possession of the Society were numerous 

 samples of diatomaceous earths, deep sea dredgings, sponges, and some 

 shells. It had been decided to dispose of these to Fellows of the Society 

 and to Members of the Quekett Club, and any Member of either Society 

 who would like to have any of the material was invited to apply as early 

 as possible to the Assistant Secretary at the Society's rooms. 



Mr. C. Baker exhibited two Microscopes, one being specially made 

 for critical work, having pull and rack draw-tubes, mechanical stage, and 

 substage with fine adjustment. It was also interesting in being fitted 

 with the Society's new size eye-piece, gauge No. 3 of 1 • 27 in. The other 

 instrument, called the Plantation Microscope, was designed for use in the 

 tropics for the purpose of discovering the ova of internal parasites ; being 

 made in the simplest possible manner, it could be used by any person 

 not acquainted with microscopical technique, and having a magnifying 

 power of x 150, would be found efficient for the diagnosis of over half-a- 

 dozen kinds of ova. 



The President said he was pleased to hear of the adoption of the new 

 1 • 27 eye-piece by Messrs. Baker, and a vote of thanks to them for sending 

 these exhibits was unanimously passed. 



Dr. Hebb said another paper had been received from Mr. F. W. 

 Millett, being Part VIII. of his series of papers on the Foraminifera of 

 the Malay Archipelago. He stated that, as on former occasions, this 

 paper would be taken as read, and that it would be published in due 

 course in the Society's Journal. 



The thanks of the Society were voted to Mr. Millett for his 

 communication. 



Mr. E. M. Nelson read a paper " On the Lag in Microscopic Vision," 

 which he illustrated by drawings and by a series of tables showing the 

 proportionate values of the performance of various objectives under eye- 

 pieces of different powers. In the case of an apochromatic objective of 

 fine quality the degree of merit was shown to range from 14 ■ 7 with a 

 low eye-piece to 7*7 with a deep one, but the difference was more 

 marked in the case of dry lenses of ordinary achromatic construction. 

 Mr. Nelson said that his experiments had shown that in respect to the 

 lag, short-tube Microscopes had some advantage over those with long 

 tubes ; contrary to what he had previously thought, it appeared that 

 lengthening the tube increased the lag. 



The President said they would be very glad to read this paper in 

 extenso, as from the simple results arrived at by a path of mathematical 

 deduction which Mr. JNelson had put before them, it was one likely to 

 prove of great practical value. 



The thanks of the Society were voted to Mr. Nelson for his paper. 



Mr. E. M. Nelson also read a paper for Mr. E. B. Stringer " On a 

 New Form of Fine Adjustment," a Microscope by Messrs. Watson 

 and Sons fitted with the arrangement being exhibited in illustration. 



