16 CHILLED lEON. 



lute faith in any particular make of pig iron is likely to be 

 at times ill-requited. 



Occasional physical testa, accompanied with chemical 

 analyses of irons used for chilling were advocated, and the 

 author was of opinion it would bo well whenever a chilled 

 casting had enjoyed a good reputation for standing up to 

 its work, that when it was retired from service some por- 

 tions of it should be chemically analysed, so as to obtain 

 clues to compositions of excellence. Great advantage would 

 ultimately arise from a comprehensive series of such exam- 

 inations. 



Some of the physical characteristics of chilled iron, as well 

 as the surprising locomotive properties of carbon present in 

 heated iron, were noticed. Attention was called to some 

 Goi'man data, published by Dr. Percy in 1864, concerning 

 an iron which before molting weighed (approximately), 

 448.^ lb. per cubic foot, and contained (approximately) 4 per 

 cent, of carbon (^ being graphitic, and £- combined). The 

 chilled portion of a casting from this had a specific gravity 

 equivalent to 471 lb. per cubic foot, and contained 5 per cent. 

 of carbon, all combined. The soft portion of the same cast- 

 ing weighed 447f lb. per cubic foot, and contained .'JJ per 

 cent, of carbon (3;,- being graphitic and f combined). Mr. 

 Morgans doubted whether so great an increase in density 

 often arises from chilling. Tool stcel,whcn hardened by being 

 chilled in cold water, docs not become condensed, but sliglitly 

 expanded from the bulk it possesses when annealed or soft. 

 Here an increase of hardness is accompanied by a decrease of 

 density. The gradual development of a network of cracks 

 over the face of a chilled anvil or bit being used in tilt 

 hammers was mentioned. Such minute cleavages become 

 more marked as tlie chill is worn down by work and from 

 grinding. Traces of the same occurrence are observable 



