222 DISCUSSION AT SHEFFIELD 



Mr. J. N. Greenwood referred to the difiiculty of discussing 

 the many points at issue. First of all there was the perfecting of 

 the design of the optical system of the microscope itself. That was 

 definitely a question to be tackled by the opticians. On the other 

 hand there was the question of the use of the microscope, and in 

 that connection there were very great improvements necessary in a 

 good many cases. As regards the question of vibration, one speaker 

 suggested that the people who supply the microscopes should supply 

 some means of getting over this trouble. But the trouble could only 

 be rectified by each user of the microscope himself, because at the 

 various laboratories where the microscope was found the component 

 vibrations were ditYerent. Sometimes it was the vertical which pre- 

 ponderated and sometimes the horizontal, and the question of the 

 situation and the type of machinery close by had to be gone into 

 before the vibration should be overcome. 



As regards magnification, a good many metallurgists were ex- 

 pecting more from the microscope than was likely to be forthcoming 

 in the near future. As far as he could see, unless there were some 

 absolutely new development in the way of objectives we were not 

 likely to get anything approaching the increase of magnification 

 and resolving power which some metallurgists desired. Magnifica- 

 tions of 1,500 were now quite possible, and every one obtained them 

 more or less easily. But to get at the bottom of such problems as 

 })rittleness and cold working we should have to get far beyond what 

 we had been doing and approach molecular dimensions : even at t«n 

 thousand we were still a very long way from seeing molecules. It 

 seemed to him that something like 100,000 would be nearer 

 the mark, and he could not see how from the present system and 

 using reflected light that we were likely to get anything of that order. 

 If the opticians gave us 10,000, then they would have reached 

 their limits with the present methods. He thought there was more 

 prospect of getting information by examining other physical proper- 

 ties apart from or in conjunction with the microscope. He con- 

 cluded by saying that during the past five weeks he had given more 

 time and study to the microscope than he had during the last five 

 years, so that in fixing attention on points like this, such dis- 

 cussions are invaluable, because few people had time to gather 

 iaformation of this kind. 



Note added March ^iJi. — It has been suggested that I am pessi- 

 mistic with regard to possibilities of higher magnification. I do 

 not wish to convey the idea that I do not look for any improvement 

 in magnification, but rather than in the two problems mentioned 

 the probable improvements in the microscope will scarcely go far 

 enough. On the other hand, there is an enormous field of utility 

 for magnifications (with correspondingly high revolving power) of 

 the order of 5,000, in defining the structures of special steels. 



Mr. G. R. Bolsover said the papers resolved themselves into 

 three types. A certain section dealt with the historical side, 

 another with the utility of the microscope, aud the third with the 

 microscope as an instrument. The historical side was dealt with 

 mainly by Sir Kobert Hadfield in two papers. He suggested that in 



