224 DISCUSSION AT SHEFFIELD 



The Chairman : Dr. Tkompson refers to the Reicliert microscope, 

 and says very good results can be obtained when the disc illuminator 

 is used instead of the pair of prisms ordinarily fitted. Does he 

 know whether such a microscope has been made by Reichert? 



Dr. F. C. Thompson: Benedicks has adapted one himself for 

 that purpose 



The Chairman : Another point is with regard to vibration, and 

 regarding this I would point out that Dr. Rogers would not use a 

 four-metres extension if his apparatus was established near . a steam 

 hammer. Usually in a works it is necessary to use a short extension 

 for this reason. 



Dr. F. Rogers: There is a good deal in that. I am glad that 

 the discussion is touching on the question of vibration. It has 

 been suggested to me that the whole apparatus should be afloat on 

 water or oil. It seems to me a rather good idea, but I don't sug- 

 gest that you should have to swim to it. I have not worked out th.© 

 detail, but I think the problem will be ultimately solved in that 

 way, perhaps combined with springs or india-rubber moorings. 



Dr. W. H. Hatfield: Arising out of this discussion there is 

 one thing I should like to say with regard to my experience. I 

 have done a great deal of photomicrography, and for one period 

 of something like six or seven years I used a Watson microscope. 

 Now, that microscope cost about 50 to 55 guineas, whereas the Zeiss 

 cost about 100 guineas. I produced well-nigh perfect pictures at 

 1,000 and slightly over. In fact, the work v/as equal to that given 

 by the Zeiss, and I shall be glad to show anyone the slides. I 

 mention this because so much has been said about the German 

 manufactured article being better than the British, and I think it 

 is oniy fair that we should put that on record. 



Mr. L. Dufty drew attention to the different magnifications 

 given in the various papers, and suggested that it would be a great 

 improvement if standard magnifications were adopted. Another 

 thing that should be stated in the papers was what objectives and 

 eye-pieces were used. It would be a great advantage if these were 

 given when stating the magnifications. 



The Chairman : The matter of standard magnifications is men- 

 tioned in Sir Robert Iladfield's Introductory Address. The Ameri- 

 can Society for Testing ]\laterials has issued a list of standard magni- 

 fications which, as far as my recollection goes, runs in fifties. It is 

 open to every investigator to work to simple, round figure, magni- 

 fications. 



Mr. L. Dufty : Yes, but you will see investigators often work in 

 anything except round figures. 



