228 DISCUSSION AT SHEFFIELD 



Dr. F. C. Thompson said it was at times very difficult to confine 

 oneself to given magnifications. The Institute of Metals had brought 

 out a list of magnifications seven or eight years ago, and authors 

 of papers were requested to confine themselves to those standards, 

 but no attempt appears to have been made by the Publication Com- 

 mittee to enforce these, and he did not think they were being 

 observed now. 



With regard to stands, in his experience the English stand was 

 absolutely unsurpassed. They had some very old Beck stands at the 

 University which had been subjected to extremely hard work, and 

 even now those stands were in excellent condition. The samei applied 

 to geological and other stands by Watson's, which were being sub- 

 jected to equally hard work. They appeared to be a distinct im- 

 provement on anything that foreign countries could supply. 



With regard to objectives, the position was not quite the same. 

 For lower power English objectives were most admirable, but he 

 agreed with Mr. Monyjoenny that above one-sixth the Zeiss was 

 much better. Dealing with illumination, the arc lamp, if it was 

 working well, did quite admirably. Small arcs, however, were very 

 unsatisfactory. If it were not for the increased amount of atten- 

 tion required, the ideal illuminant was the lime light. One got 

 large area of illumination of high actinic value if one took the 

 necessary trouble. 



A Member remarked that if a standard for magnifications was 

 fixed there should also be a standard of objectives for each magnifi- 

 cation. 



The Chairman : On this matter of standard magnification this 

 Association might very well have the views of all our members using 

 microscopes ascertained and a memorandum prepared, 



Mr. F. S. Spiers said that an important factor in determining 

 the size of reproductions was that of cost. Anyhow, that placed an 

 added difficulty in the way of standardisation. With the permission 

 of the meeting he would like to bring up the subject before the Council 

 of the Faraday Society, and perhaps some steps might be taken 

 in the direction of standardisation. There were one or two things 

 mentioned in the discussion in London which he thought it of 

 interest to bring forward, notably the suggestion to form a standing 

 committee to undertake proper tests of objectives now being manu- 

 factured. It was hoped that would settle once and for all the ques- 

 tion, of the merit of British objectives. 



The Chairman : It appears that members of our Association 

 are not quite unanimous on certain points. In the first place, as 

 regards the question of disc versus prism illumination. I may have 

 been" unfortunate in my experience of prisms, but I always find 

 that I can get better photographs with even ordinary covered glasses 

 than from any prism, and, judging not only by my own results, but by 

 those of my friends, I must say the glass disc illuminator is much 

 to be preferred to the prism. The other point on which there is 

 a sharp difference of opinion is with regard to illuminants. I have 



