390 PROCEEDINGS OF THE 



extraordinary rays, and from the relation between the refractive 

 index of calcite and that of the extraordinary ray this ray went 

 nearly straight through the polariser, and emerged as a plane 

 polarised beam of light, whose vibrations were parallel with the 

 short axis of the Nicol's prism, this being the principal way of 

 obtaining plane polarised light. Also the ordinary ray for a 

 similar reason could not pass through the polariser beyond the 

 dividing plane cemented with Canada balsam, but was refracted 

 at the surface of the balsam and lost. The analyser, which is 

 a prism similar to the polariser, treated rays of light in the same 

 way, and there the emergent rays vibrate again parallel to the 

 short axis of the Nicol ; only doubly refracting material is effective 

 for observation with polarised light, because unless it is doubly 

 refractive interference cannot be obtained, and therefore no 

 colour due to polarisation occurs. The President said it was 

 fortunate that Mr. Ingpen's gift had formed a subject for an 

 address on polarised light, and he suggested a hearty vote of thanks 

 to Mr. Grundy for his explanation ; this was given unanimously. 



At the 529th Ordinary Meeting of the Club, held on Decem- 

 ber nth, 1917, Vice-President D. J. Scourfield, F.Z.S., F.R.M.S., 

 in the chair, the minutes of the meeting held on November 13th 

 were read and confirmed. 



Messrs. Edward Hight and Evan V. Pike were balloted for and 

 duly elected members of the Club. Nomination forms for two 

 candidates were read for the first time. 



The chairman announced that Mr. C. F. Rousselet had presented 

 to the club several portraits, and also a further collection of photo- 

 graphs of drawings of Rotifera to be added to those he had already 

 given. He said that Mr.Rousselet's health was slightly improved, 

 and expressed the hope that it might in time be sufficiently 

 restored to enable him again to attend the meetings of the Club. 

 Mr. Bryce drew the attention of workers on the Rotifera to the 

 very valuable collection of drawings that Mr. Rousselet had 

 placed at their disposal. He said that there were among them 

 figures of many forms not described in Hudson and Gosse's work, 

 and urged the members to make use of them. 



The Hon. h'ecretary announced that there would be no meeting 

 on December 25th, and that at the meeting on January 8th 



