26 INTRODUCTORY ADDRESS: 



require extraordinary en re in the etching or otherwise the structure 

 will vary considerably and be misleading. Some alloys, for example 

 St^el containing high percentage of Nickel, are not attacked by any 

 ordinary etching reagent. 



All honour to Sorby, the man who led the way in this branch of 

 Science, and started us, who are to-day benefiting in such a remarkable 

 manner from the knowledge he first originated and obtained in this 

 important and complex branch of Science. All honour, too, to the 

 band of willing workers who have accomplished such great progress, 

 ^nd who have surmounted the many difficulties in their path. 



SECTION v.— STANDARD MAGNIFICATIONS FOR 

 PHOTOMICROGRAPHS. 



The question of the Standardisation of Magnifications for Photo- 

 micrographs of Metals and Alloys has been given a certain amount of 

 discussion both in this Country and in America. 



Committee E-4 of the American Society for Testing Materials has, 

 in fact, drawn up tentative '"' Definitions and Rules governing the 

 Preparation of Micrographs of Metals and Alloys," which include 

 Standard Magnifications for general use, and Ferrous and Non-ferrous 

 Metals. I have brought this matter before the British Engineering Stan- 

 dards Association, who are considering the subject. The Institute of 

 Metals in this Country in its "Notes for Authors " also specify cer- 

 tain Standard Magnifications which it is desired Authors should use. 



Whilst not wishing in any way to hamper the Research Worker, 

 there are reasons why it seems strongly advisable that for general 

 purposes Standard Magnifications should be adopted for the Photo- 

 micrographs. Very little quantitative data is forthcoming from the 

 micro-examination of metals. Where the grain size can be determined, 

 this is often distinctly useful and worth recording. For the most 

 part, however, the Microscopist is dependent on a trained eye, re- 

 ■sulting from prolonged experience in the examination of micro- 

 structures to aid him in their interpretation. It would seem reasonable, 

 therefore, that the magnifications used should be standardised and as 

 few as possible, in order that comparisons between the structures of 

 different specimens may h^ facilitated. 



I would therefore like strongly to urge that the various Societies 

 interested in M^^tallography should join in drawing up rules governing 

 the reproduction of photomicrographs, which should be of certain 

 Standard Magnifications and naturally should be reproduced full size. 



Surely there is every reason for having an International Standard; 

 at any rate, Great Britain and America could work together. It 

 might well, indeed, be made a matter for Allied consideration, or 

 one for consideration in connection with the movement for the 

 formation of International Unions in which the Conjoint Board of 

 Scientific Soc'eties is interestinsr itself. 



