HAMIIvTON SCIi^NTIFIC ASSOCIATION 47 



1826, when Seth Boyden, of Newark, NJ., started a foundry 

 for the production of harness hardware and other castings of 

 small size. Since that time it has grown to very large pro- 

 portions, and the uses of the material have greatly extended, 

 until at the present time its foundries are engaged in turning 

 out castings varying in weight from a few ounces to several 

 hundred pounds, and adapted to as wide a variety of require- 

 ments. It would be impossible to enumerate a list of the uses 

 to which it is put, but it may be stated, in a general way, 

 that it enters very largely into the construction of many lines 

 of machinery, of which agricultural implements may be taken 

 as a type. It is also extensively used in the building of rail- 

 way cars, and it is only recently that steel has been sub- 

 stituted for malleable iron in car couplings. 



The value of malleable iron, as a material of construction, 

 lies in certain special properties which are, in a sense, inter- 

 mediate between those of ordinary gray cast iron on the one 

 hand, and mild steel on the other. Its most valuable 

 properties are the readiness with which it may be machined, 

 a fairly high strength under tensile strain, a considerable 

 degree of ductility, and a consequent ability to withstand im- 

 pact strains under working conditions. It may be readily 

 bent, and castings may, therefore, be adapted without 

 difficulty to the positions in which they are to be used. In 

 these, respects malleable iron is undoubtedly inferior to mild 

 steel, and steel castings are therefore in demand for uses in 

 which the conditions are more severe, as for example, in the 

 case of the car couplings already cited. But the difficulties 

 attendant upon making them, and the consequent higher cost 

 of their production limits their application to situations where 

 higher strength is of the utmost importance. Ordinary gray 

 cast iron, on the other hand, while it is cheaper than malleable 

 iron, and while it is admirably adapted for use under com- 

 pression, is incapable of withstanding severe shock, will not 

 bend, and is unsuited to working under tensile strain. 



For the purpose of illustration there is given in Table i 

 a statement of the ductility and tensile strength per square 



