323 



Dr. G. D. Brown said that having seen the slide he could say that it 

 seemed to him to be a very admirable contrivance for the purpose. 



Kef erring to the discussion which took place at the last meeting with 

 respect to microscope tables, Mr. Mainland suggested that the best substi- 

 tute for a revolving table was one of the highly lacquered Japanese trays 

 now so common in this country, recommending that one should be chosen 

 for the purpose, about 20in. X 12in., as flat and true as possible. The 

 microscope, lamp, &c, might be placed upon this, and being adjusted could 

 be passed along the table with the greatest ease. The advantage of this 

 plan was that the microscope was raised as little as possible above the 

 table, whilst the rim of the tray served the double purpose of affording 

 something to take hold of and keeping the accessories from getting swept 

 off the surface. 



Mr. J. D. Hardy said he could speak from experience as to the efficacy of 

 the tray, having used one for the purpose for the last five years. It was a 

 very simple and efficacious means of keeping all one's things together, and 

 was very easily passed over the table cloth. For ordinary work it was 

 everything required. 



Mr. J. A. Ollard exhibited a simple form of revolving table which he had 

 made out of two mincing boards. 



Votes of thanks to Mr. Stokes, Mr. Moreland, and Mr. Ollard, for their 

 communications were unanimously passed. 



Mr. A. D. Michael said that some time ago he had a concave mirror 

 constructed of opal glass, and found that whilst it answered the purpose of 

 giving clear definition there was a considerable loss of light. In endeavour- 

 ing to account for this it occurred to him that it might be due to some of 

 the light being more or less polarized. In order to test this he put on the 

 analyser, and was rather surprised to find how efficiently the light was 

 polarized. They were well aware, no doubt, that light could be polarized 

 in various ways, such as with a Nicol prism, or by reflection at a particular 

 angle, or by passing it through thin plates of glass set a similar angle. He, 

 therefore, thought that he must have got his microscope inclined at just the 

 polarizing angle, but on altering it the effect did not go off as he had 

 expected, and in fact he found that he got polarized light at almost any 

 angle. The effect was just the same if he substituted for the mirror a piece 

 of white china or a white dinner plate, and the first question which occurred 

 to him was, why was light polarized in this way by reflection from some 

 substances and not from others ? His microscope was in the room with an 

 analyser upon it, and being adjusted at haphazard they would be able to see 

 for themselves what he had described. It might be asked cui bono ? and 

 perhaps there was not much good in it, though a full field of light was 

 obtained. He did not claim any speciality, but thought the matter was 

 sufficiently interesting to warrant him in bringing it before the meeting. 



Mr. Stokes enquired if more light was obtained in this way than with a 

 prism ? 



Mr. Michael said this was the case. 



Mr. C. Stewart asked if the blackness of field was equal to that obtained 



