of Bronzes from Machu Picchu, Peru. 595 



zonal structure. The general effect at this magnification is 

 shown in fig. 91. All parts of the section look very nearly alike, 

 but, under the higher powers, it is seen that the deformational 

 characteristics are more pronounced in the vicinity of the 

 edge; the cores, or zones, themselves show elongation near the 

 edge and lines of deformation are abundant, both in the frag- 

 ments of the primary grains and in the recrystallized grains. 

 The structure of this portion is shown in fig. 92 at a magni- 

 fication of 220 X- Owing to the selective etching in copper- 

 rich zones, the finer detail cannot be brought out with uniform 

 clearness all over the surface; if the etching is carried far 

 enough to bring out the detail in the light zones, it will be 

 obscured in the dark zones (fig. 91) ; if it is only carried far 

 enough to bring out the detail in the dark zones, there will be 

 very little detail in the light zones, as in the present instance, 

 fig.' 92. 



Scleroscopic tests confirm the micrographic conclusions, in 

 that they show a maximum hardness number of 27 near the 

 edge (%" from the extreme edge) and a lower number, 15-16, 

 in the body of the chisel. The grain count of 55, which was 

 originally obtained at 220 X and recalculated for the standard 

 magnification, 72 X? is only approximate but indicates, in con- 

 nection with marked residual inhomogeneity, that the chisel 

 has received only very light annealing treatment. From the 

 character of the zones, in particular their equiaxed appearance, 

 except near the very edge, it is clear that the present form of 

 the object is not widely different from that of the casting used 

 in making it. 



Object No. 17 (cf. Table I). 



This object is described in Table I as an irregular mass. 

 The surface illustrated in fig. 25 is covered with large and small 

 warty excrescences, while the opposite side is smooth and 

 partially rounded at the edges. It is not improbable that the 

 object is, in reality, a button which was left in the pot, or 

 crucible, after pouring a heat of metal. In conformity with 

 this assumption, the grain, as shown in fig. 91, at 12 X and 

 in fig. 95, at 72 X, is coarse enough to indicate comparatively 

 slow cooling. The tin-rich zones appear dark in both photo- 

 micrographs owing to their rounded character after etching and 

 the corresponding inequalities of focus. Some patches of the 

 a -f- 8 complex may be seen when the specimen is examined 

 with the higher powers. Experiments with small castings of 



