628 SUMMARY OF CURRENT RESEARCHES. 



National Physical Laboratory.* — Metallographical research work 

 lias been carried out upon the constitution of the aluminium-zinc- 

 copper alloys, the effects of strain at high temperatures, and the inter- 

 crystalline cohesion of metals. The new copper-depositing reagent for 

 etching steel has been in constant use, and has given important results. 

 An annealed steel, showing phosphoric banding when etched with the 

 new reagent, was heated to 800° C. and quenched. It then consisted 

 mainly of martensite-troostite, but certain regions consisting of ferrite 

 were identified with the phosphoric bands of the original annealed steel. 

 Their relatively high phosphorus-content had prevented the diffusion of 

 iron carbide into the bands. 



* National Physical Laboratory, Report for year 1914-15. 



