J. L. Smith—Mass of Meteoric Iron. 393 
far those substances usually called impurities in iron are to be 
regarded as hurtful. The tendency of the investigations at the 
present time is to show that these supposed impurities may all 
_ Play an important part in useful modifications of iron, when 
present even in very minute quantities; and I would state, as 
the result of my observation (and one bearing upon the present 
question), that one per cent or less of phosphorus so far modi- 
fies cast iron that it will resist the action of concentrated sul- 
‘ge have to make trial of many descriptions of cast iron 
efore they can get one well adapted to their pu ose ; Some 
ing destroyed in a few weeks, while others 
verifi equent anal wa in 
oo ee as oi 
usi 
tron, but that the portions of i 
crystals babdaive cue richly charged with phosphorus, from the 
