52 



Mr. Hardy thought that it might probably be made for about 10s. ; the 

 one he exhibited had been made only for his personal use. 



Mr. Ingpen hoped Mr. Hardy would excuse him for hinting that this came 

 rather near to Mr. Wenham's paraboloid compressor ; the method of hing- 

 ing the cover was certainly a great improvement. 



Mr. Hardy thought it made all the difference whether it worked on a hinge 

 or on a pivot. 



Mr. Ingpen said that for use with the paraboloid the lower glass should 

 be made as nearly flush with the base-plate as possible ; many compres- 

 soriums were unsuitable in this respect. In Abbe's condenser the top lens 

 came up almost to the surface of the stage. A drop of water between the 

 lens and the slide gave a blacker ground. If he were right in his idea that 

 Abbe's condenser was the condenser of the future, those who were devis- 

 ing new forms of apparatus would do well to bear this in mind. The com- 

 pressor exhibited by Mr. Hardy was very beautifully made, and quite 

 capable of performing all that was claimed for it. 



Mr. Michael said that he regarded the substitution of a hinge for the 

 pivot as a great point, the pivot being very liable to damage the specimen 

 by slipping ; for when they had a delicate object to examine they must leave 

 it wherever it might be well displayed. He thought, however, that the 

 screws would be likely to interfere with the free movement of the objective 

 over them. 



Mr. Hardy said he had used it with a f-in. objective. 



Dr. Matthews said there was another form of compressorium which had 

 the merit of moving with a parallel motion — he referred to the Boss form 

 — it was impossible with this instrument to destroy an object by lateral 

 motion, whilst the field was large enough to allow of the examination of an 

 object even if it did not happen to be near the centre. 



Mr. Ingpen said he had used this compressorium for years, and considered 

 it to be one of the most useful. With regard to keeping lively objects in 

 the middle of the glass, Dr. Hudson had adopted the plan of surrounding 

 rotifers with a few threads of cotton wool, which he found very useful in 

 preventing them from straying about the field. 



Mr. Stewart said he had often used cotton wool in examining rotifers 

 and had found it exceedingly useful ; but prepared cotton wool, from which 

 all fatty matter had been extracted, should be used for the purpose. 



The thanks of the meeting were voted to Mr. Hardy for his communica- 

 tion, and the proceedings terminated with the usual Conversazione, at which 

 the following objects were exhibited : — 



Head of a House-spider, Ciniflo similis, male Mr. F. Enock. 

 Bamboo fibre, polarized ... ... ... Mr. H. R. Gregory. 



Yolvox globator, infested with Notommatal 



., \ Mr. J. E. Ingpen. 



parasua ... ... ... ) ot ^ 



Section of Serjanus, illustrating the use of-\ 



polarized light as a means of differentia- > ]y; r# ^. j), Michael. 



tion instead of double staining ... J 



Attendance — Members, 37; Visitors, 2. 



