of Bronzes from Machu Piccliu, Peru. 577 



Object No. 2 (cf. Table I). 



The small object shown in fig. 10 was cast in substantially 

 its present form. As in the case of the preceding piece, the 

 casting has been somewhat altered by cold-working. The altered 

 portions are the delicate elongated bird's bill and the lower 

 part of the stem, including the flattened end. As this object 

 was too smalj. to yield satisfactory drillings for analysis, a sec- 

 tion was cut from the stem for this purpose. Of the two 

 pieces remaining, the larger, including the bird's figure, was 

 embedded in plaster, ground, and polished for examination. A 

 diagram of this portion is given in fig. 40, along with other 

 figures representing the microstructure. The other piece, 

 flattened at the lower end, was thereupon flattened without 

 fracture at the other end by hammering on an anvil, thus 

 demonstrating the cold malleability of the metal. It was 

 thought desirable to make this test in view of the considerable 

 tin-content of the metal (13.45 per cent) and the comparatively 

 large amount of embrittling a -f- 8 complex. Cf., in this con- 

 nection, discussion on pages 543-545. This is shown in fig. 41 

 as a delicate light-colored constituent within the comparatively 

 broad, white, tin-rich zones which envelop the black cores. 

 Maximum heterogeneity was developed in etching by using a 

 light wash of acidified ferric chloride after the usual treatment 

 with ammonia and hydrogen peroxide. 



The casting structure is distinctly predominant all over the 

 surface of the section. The flattened end of the object had, 

 however, received a light annealing treatment between the 

 stages of cold working. This is shown by the occurrence of 

 very fine recrystallized grains, which are abundant in this 

 region, but gradually disappear as we proceed upwards along 

 the stem. Grain characteristics of this sort were developed in 

 the laboratory by annealing at 650°. It is probable that the 

 present object was annealed by thrusting the point into the 

 fire and then withdrawing it, when a dull red color began to 

 creep up the stem. 



Tests along the stem showed a scleroscopic hardness of 32-35, 

 while, within the contours of the figure at the head of the object, 

 a hardness value of 14-15 was obtained. Corresponding to 

 these results, the characteristics of deformational treatment were 

 observed only in the stem and at both ends of the object. The 

 effect of working a small casting locally in this manner can be 

 seen on the etched surface without the aid of the microscope. 

 There is a visible difference in the quality of the etching in 



