J. H. G. MONYPENNY 151 



electric furnace), and shows the development of long chill crystals. 

 Fig. 14 (from a file blank burnt in forging) was also taken by this 

 method, and shows (x3 diameters) the decarburisation Tormed both 

 in the skin and round the cracks. 



A method of illumination similar to the last one was described 

 by F. B. Foley in " Metallurgical and Chemical Engineering " 

 (August 1st, 1919). He used it for low power photomicrographs (at 

 about 7 diameters). For this purpose, however, the author prefers 

 the arrangement shown in Fig. 8, as it gives better detail at these 

 magnifications. 



In conclusion, the author wishes to thank the Directors of Messrs. 

 Brown Bayley's Steel Works, Ltd. (and in particular Mr. H. 

 Brearley) for permission to publish the photographs accompanying 

 this paper, and also to Messrs. F. S. and W. H. Nicholds (members 

 of the Laboratory Staff) for their assistance in preparing the photo- 

 graphs and diagrams. 



