478 



METALLURGY. (APPARATUS.) 



just visible as shining points of the surface, 

 which would now have a topography charac- 

 teristic of the alloys examined with its undula- 

 tions representing the variations of quality, 

 with changing proportions of the three con- 

 stituents. On the model thus formed, the po- 

 sition of the strongest alloy was indicated by 

 a distinct elevation or mountain, not far from 

 the point, copper = 55, zinc = 43, tin = 2, at 

 which the tenacity was about 65,000 pounds per 

 square inch. This gives a close-grained alloy, 

 of rich color and fine surface, and capable of 

 taking a good polish. It had immense strength, 

 and seemed unusually well adapted for general 

 use as a working quality of bronze. The alloy 

 having the highest qualities of toughness as well 

 as strength contained less tin than the above 

 composition, viz. : Copper = 55, tin = 0'5, zinc 

 = 44-5. It had a tenacity of 68,900 pounds 

 per square inch of original section, and 92,136 

 pounds on fractured area. This alloy and the 

 "Tobin alloy," copper = 58-22, tin = 2'30, zinc 

 = 39'48, are good working metals ; the latter 

 is capable of great improvement by skillful 

 working either hot or cold, and of obtaining 

 a tenacity of more than 100,000 pounds per 

 square inch. The addition of tin and of zinc 

 to cast copper increases the tenacity up to a 

 certain limit, and the influence of tin is nearly 

 twice as great; while the limit of useful effect 

 is not reached with zinc until the amount add- 

 ed becomes very much greater than with the 

 copper-tin alloys. Brasses can be obtained 

 which are much stronger than any bronzes, 

 and the ductility of the working compositions 

 of the former class generally greatly exceeds 

 that of the latter. So sensitive is zinc to the 

 presence of tin that M. Bischof states that he 

 can detect the addition of one part in tin in 

 10,000,000 of pure zinc. Prof. Thurston hav- 

 ing laid down the boundaries within which 

 the useful alloys of copper-tin-zinc are to be 

 found, Mr. Maurice I. Coster, under his direc- 

 tion and supervision, investigated the inclosed 

 field, beginning his work with two series in 

 order to fix more accurately its precise limi- 

 tations. When these were approximately de- 

 fined, three other series were proposed, in 

 which the alloys were made to differ by smaller 

 percentages. Thus the influences of slight va- 

 riations in the composition of the bronzes were 

 determined. Mr. W. Ernest H. Jobbins con- 

 tinued the investigations in the light of the 

 results obtained by Prof. Thurston and Mr. 

 Coster, choosing as his field a triangular area 

 of Prof. Thurston's map surrounding the mount- 

 ain of 65,000 pounds tenacity, which embraced 

 all that portion of the field in which the most 

 tenacious alloys had hitherto been discovered. 

 The boundaries of this field were : copper, maxi- 

 mum = 60, minimum = 50 ; zinc, 48 and 38 ; 

 tin, 5 and ; limits which included the " Tobin 

 alloy " and Prof. Thurston's alloy of 68,900 

 pounds tenacity. Of twenty-three alloys ex- 

 perimented upon, No. 22, the composition of 

 which is copper 57, zinc 42, tin 1, was deter- 



mined as the " strongest of the bronzes " ; No. 7, 

 copper 55, zinc 44, tin 1, as second in quality; 

 and No. 5, copper 56, zinc 42, tin 2, as the best 

 for practical purposes. The last is described 

 as a very fine alloy, possessing great ductility, 

 giving a good, smooth, square fracture, and hav- 

 ing the grain very close and compact. 



Cobalt-bronze is a new alloy introduced 

 Messrs. Henry Wiggin and Son, Birmingham, 

 England, to furnish a compound having the 

 desirable qualities that have heen found to 

 exist in the metal cobalt. The inventors had 

 determined that pure metallic cobalt could be 

 rolled into sheets and wrought into articles of 

 utility, but found that its high price would pre- 

 vent its coming into practical use. In cobalt- 

 bronze they claim to have preserved the ster- 

 ling qualities of the metal at a marketable price. 

 It is manufactured in several qualities, the high- 

 er grades of which are recommended for their 

 close, steel-like surfaces, their susceptibility of 

 a high polish, their suitability for casting pur- 

 poses, and their hardness, toughness, and great 

 tensile strength. 



A white bronze is coming into use for monu- 

 ments which has been found to stand exposure 

 to the weather for a very long time. The ma- 

 terial is non-corrosive and unchangeable, and 

 is therefore better adapted to certain purposes 

 than some of the more costly metallic com- 

 pounds. The monuments are cast from refined 

 zinc, and are given their sparkling appearance 

 by the sand - blast. The sand, being blown 

 against the work under a high pressure of 

 steam, cuts the surface, but does not adhere to 

 it. A film of oxide which forms on this bronze, 

 although it is so thin as to be unmeasurable, is 

 indestructible by the elements, being insoluble 

 in water and impenetrable by air. 



Mr. John S. Brodie, in a paper read before 

 the Liverpool Engineering Society on the 

 strength of bronze alloys, spoke of silicious 

 bronze as a substance, wires made from which 

 have all the tensile strength of high-clas 

 wrought-iron, with more than four times th( 

 electrical conductivity of iron. With th 

 metal, then, overhead wires might be made 

 one fourth the weight of the wires now in use. 

 The name of forgeable brass has been given 

 to an alloy composed of 60 per cent, of copper, 

 38'50 per cent, of zinc, and 1^ per cent, of 

 iron. The compound has the property of being 

 readily worked when warm. It can then be 

 employed for constructing various pieces of 

 lock-work which are commonly made of iron, 

 but which, when made of this alloy, would be 

 much less subject to rust. 



Apparatus. G. A. Forsberg describes a modi- 

 fication of the Swedish u Lancashire " hearth- 

 finery, which has been introduced at the Skuts- 

 kar Iron Works. It is of the ordinary Swedish 

 rectangular form, but has a third tuyere in the 

 back wall. The side- walls are formed of hol- 

 low iron castings, which are cooled by allowing 

 the blast to pass through them, whereby it 

 becomes heated before arriving at the tuyeres. 



