50 PEOCEEDINGS OF THE 



about the optical index of a l/6tli of 0*75 N.A,, and tMs is 

 greater than that recommended by Abbe as an id,eal amount. I 

 cannot urge too strongly all microscopists to perform this simple 

 experiment, and to study carefully the two images. The ideal 

 optical index is 25 ; a good one for practical work is 20. The 

 24 and 12 mm. apochromats of N.A. 0*3 and 0*65 are both 

 over 30, and are therefore overdone, whereas those of 16 and 

 18 mm., with the same apertures, are 20, and are about right. 



At the 539th Ordinary Meeting of the Club, held on January 

 14th, 1919, the President, Dr. A. B. Rendle, M.A., F.R.S., in 

 the chair, the minutes of the meeting held on December 10th, 

 1918, were read and confirmed. 



Messrs. Fredk. Thos. G-ummer, Wm. Battle and W, S. Warton 

 were balloted for and duly elected members of the Club ; four 

 nominations were read for the first time. 



Dr. Rendle read out the list of nominations for officers for the 

 coming season, and great satisfaction was expressed that he 

 had again consented to be nominated to the presidency. Four 

 members were nominated to fill the vacancies on the committee 

 caused by the retiring of the four senior members, and the 

 election will take place at the next meeting. 



The President announced the death of Mr. L. C. Bennett, 

 which took place just before Christmas. Mr. Bennett was well 

 known to those members who attend the Club's meetings. In 

 consequence of the Secretary's absence at the beginning of the 

 meetings in the committee room, Mr. Bennett undertook to 

 look after new members and introduce them to the Club. The 

 kindly way in which he performed this office did much to promote 

 the feeling of good fellowship in the Club, and his loss will be 

 keenly felt by the members. Those present expressed their 

 sympathy with Mrs. Bennett in her bereavement. 



The following gifts to the Club were gratefully acknowledged : 

 — Six slides from Mr. Evens ; two slides of diatoms in " realgar " 

 from Mr. Bowtell; and two photographs, taken by a member 

 at one of the Club's excursions in 1890, from Mr. Chipps, 



The Secretary announced that there would be a Gossip Meeting 

 on January 28th, and that the Annual General Meeting would be 

 held on February 11th, when Dr. Rendle would deliver his presi- 



