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when the announcement was made that Dr. Cooke had kindly 

 promised to write this paper, a very hearty vote of thanks was 

 given to him in anticipation, and now that it had been read he 

 was sure they would not only renew their thanks but would also 

 pass a no less hearty vote of thanks to their honorary Secretary 

 for reading it. 



Mr. E. M. Nelson described by means of diagrams drawn on 

 the board the construction of a new form of eyepiece which wa& 

 shown to possess some advantages over those in common use. 

 The theory on which the Huyghenian and other eyepieces were 

 constructed was also explained, and the differences between these 

 and his new form were very clearly pointed out. 



The President was sure the members would be very much 

 obliged to Mr. JSTelson for the explanations he had given. As 

 regarded the new eyepiece he could say that he had enjoyed the 

 opportunity afforded him of using one, and could only say that 

 he found the No. 12 a simply delightful eyepiece to work with. 

 He tried hard, but could not find any difference between this 

 and the compensating eyepiece when used with an apochrompctic 

 objective. 



Mr. Neville would like to thank Mr. Nelson for the way in 

 which he had explained these eyepieces; he had usually managed 

 to soar above their heads in the region of mathematics, but this 

 time he had come down more to the level of most people, and 

 had given them not only a simple description of how the best 

 definition was obtained, but the best mathematical explanation 

 also. He had himself been dabbling a little in optics, but working 

 by rule of thumb, and had given some attention to eyepieces, and 

 had tried to get as good an eyepiece as possible with a large field. 

 He had done this by taking an ordinary eyepiece and bringing 

 the lenses much closer together than usual, and this increased 

 the field considerably. Mr. Levy had a short time ago exhibited 

 an eyepiece at one of their meetings which immediately arrested 

 his attention from its excellent definition and its very large field, 

 it was so good that he hoped Mr. Levy would tell them how it 

 was constructed. He was very glad to find that so much attention 

 was now being given to the subject, for he thought it most 

 important that they should have good eyepieces as well as good 

 objectives. Some time ago, when they had a number of micro- 

 scopes in the room, he could not help noticing the very limited 



