of Bronzes from Machu Picchu, Peru. 579 



by the prevailing porosity. The massive grains of a are 

 attacked only superficially, resulting in the formation of a thin 

 patina. Consequently, the very considerable oxidation which 

 has affected only those objects which contain a comparatively 

 large amount of the complex (this specimen and the one num- 

 bered 5) is confined to this structure element and its path may 

 be plainly followed under the microscope. Reference has been 

 made above to the oxidation cavities of fig. 45. In this photo- 

 micrograph, neighboring patches of unaltered complex are 

 visible and the general similarity in appearance leaves no 

 doubt as to the nature of the material which originally filled 

 the dark cavities. In fig. 42, an altered patch is shown under 

 higher power (300X)- This may be compared with the light 

 patch shown in fig. 43. Small bright particles of residual h 

 are seen. A number of stages in the process of alteration were 

 observed. The a constituent is attacked first, but oxidation 

 ultimately extends throughout the complex. 



The sulphide constituent, undoubtedly Cu 2 S, is unattacked 

 by any of the etching agents used, but, while it is left bright, 

 it may be distinguished from the silvery 8 by its bluish-gray or 

 slaty color. The distinction may be made without difficulty 

 in photo-micrograph, fig. 43. Here, the sulphide constituent 

 is a little darker than the neighboring 8. Three rather large 

 rounded units are seen closely grouped at the extremity of the 

 thin projecting branch of the main patch of complex and one 

 unit half-way down this branch. In fig. 42, where the complex 

 has been altered so as to appear dark, the sulphide constituent, 

 in the shape of three units somewhat larger than those of fig. 

 43 (two, very close to one another above the center at the left, 

 and one, below the center at the right) is particularly prominent 

 by reason of enhanced contrast. The amount of sulphide in 

 this object is inconsiderable and sulphur was not reported in 

 the analysis. It always occurs in association with the com- 

 plex, usually as a neighboring constituent, but, sometimes, 

 completely enveloped by the latter. Accordingly, cuprous 

 sulphide is appreciably soluble in the (3 liquid solution and 

 most of it separates when this solution begins to crystallize. 



Object No. 3 (cf. Table I). 



This is a symmetrical and well-shaped pointed object about 

 12" long, of the type commonly used to fasten the outer gar- 

 ment. As may be seen in the illustration, fig. 11, it has a 

 six-pointed star-shaped head and tapers gradually to the rather 



