588 C. H. Mathewson — Metallographic Description 



the metal which forms the shank and blade. It is seen from 

 the two sections, a and b, of fig. 65, which are parallel and 

 about one sixteenth of an inch apart, that the central core bends 

 over at the top and develops an appendage which is also 

 embedded in the second metal. Such a complicated fitting 

 could only be obtained by flowing the outside metal around 

 the inner piece. The general shape and appearance of the 

 aperture indicates that it was left in casting. Naturally the 

 details of this interesting casting practise cannot be described. 



Object No. 8 (cf. Table I). 



Only a single section was cut from the axe illustrated in 

 fig. 16. The position of this is shown in fig. 68, and the 

 structure well under the skin in fig. 69 of the same plate. 

 The most striking feature of this photo-micrograph is furnished 

 by the large amount of cuprous sulphide which is normally 

 bluish-gray in appearance but has fallen away in places, as a 

 result of grinding and polishing, leaving black pits. According 

 to the analytical results given in Table I, there is 0.44 per 

 cent of sulphur in this specimen, a value which corresponds 

 to about 2.2 per cent of cuprous sulphide. By comparing the 

 present photo-micrograph with the preceding one, fig. 07, 

 which illustrates the structure of the copper-rich metal in the 

 knife just described, a good idea of the value of the microscope 

 in estimating the sulphur-content of a bronze may be obtained. 

 A trace of sulphur was indicated in the qualitative examination 

 of this knife. It is plainly evident in fig. 67 ; less abundant 

 and structurally finer than in fig. 69, but of the same general 

 characteristics. 



In spite of the large amount of sulphide contained in this 

 object, its cold- working properties are retained to a surprising 

 degree. A piece measuring 9X^X16 mm. was cut from 

 the head of the axe and cold-rolled in several passes to a 

 round rod 4 mm. in diameter and 35 mm. long. Further 

 extension could not be obtained without fracture. As a result 

 of this treatment, the particles of sulphide have adapted their 

 own shape to the changing form of the bronze matrix and now 

 appear elongated without evidence of fracture. (They do not 

 show cracks or fissures on the polished surface.) The photo- 

 micrograph, fig. 87, which represents this condition, was taken 

 after momentary annealing at a full red heat. 



The coarse grain of fig. 69 indicates that the object has 

 been thoroughly annealed at a temperature not lower than 



