Numerous tests of the Chapin irons have been made by competent and disinterested parties, and the results published.  The samples here noted were cut and piled only once from the muck bar.

Sample A was made from No. 3 mill cinder pig.

Sample B was made from No. 4 mill pig and No. 3 Bessemer pig, half and half.

Sample C was made from No. 3 Bessemer pig, with the following results: 

Sample.                  A         B         C
Tensile strength per sq. in.    56,000    60,772    64,377
Elastic limit.                  34,000      ....    36,000
Extension, per cent.              11.8      ....      17.0
Reduction of area, per cent.      65.0      16.0      33.0

The tensile strength of these irons made by ordinary puddling would be about 38,000, 40,000, and 42,000 respectively, or the gain of the iron in tensile strength by the Chapin process is about fifty per cent.  Not only so, but these irons made in this manner from inferior pig show a higher elastic limit and breaking strain than are commonly specified for refined iron of best quality.  The usual specifications are for refined iron:  Tensile strength, 50,000; elongation, 15 per cent.; elastic limit, 26,000; reduction, 25 cent.

Thus the limits of the Chapin iron are from 12 to 20 per cent. above those of refined iron, and not far below those of structural steel, while there is a saving of some four dollars per ton in the price of the pig iron from which it can be made.  When made from the best pig metal its breaking and elastic limits will probably reach 70,000 and 40,000 pounds respectively.  If so, it will be a safer material than steel under the same working strains, owing to its greater resilience.

Such results are very interesting in both a mechanical and economical point of view.  Engineers will hail with delight the accession to the list of available building materials of a wrought iron at once fine, fibrous, homogeneous, ductile, easily weldable, not subject to injury by the ordinary processes of shaping, punching, etc., and having a tensile strength and elastic limit nearly equal to any steel that could safely be used in the same situation.

A plant for the manufacture of Chapin iron is now in course of erection at Bethlehem, Pa., and there is every reason to believe that the excellent results attained in Chicago will be more than reached in the new works.—­Proceed.  Jour.  Asso. of Eng.  Societies.

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CELLULOID.