of Bronzes from Machu Picchu, Peru. 583 



twinning are not well enough understood at present to permit 

 any clear identification of such, phenomena. It is possible that 

 the rough edges of the pin as cast were dressed in such manner 

 as to overstrain the metal. In such case, recrystallization with 

 twin formation would have occurred on annealing. There is, 

 however, no evidence that the object has ever been annealed. 

 Moreover, a dressing of this sort would almost certainly pro- 

 duce corresponding alteration of the adjacent metal and prob- 

 ably of the metal below the pin. There is, however, no 

 recrystallization in these parts. In conclusion, it must be 

 admitted that no clear explanation of the segregated twin- 

 formation which has occurred in this object can be offered. 



Object No. 5 (cf. Table I). 



This object is the finest example of casting practise fur- 

 nished by the entire collection. As may be seen in fig. 13, 

 it represents a knife of some sort surmounted by an ornamental 

 group comprising a prostrate fisher-boy with line and fish. 

 The metallographic description of this specimen may be made 

 very brief. A section through the body and head of the figure 

 shows a characteristic casting structure. The outline of this 

 section is given in fig. 53, and the corresponding photo-micro- 

 graph in fig. 54. Corresponding to the high tin-content of the 

 object some patches of a -j- 8 complex may be seen within the 

 tin-rich matrix even under the moderate magnification chosen 

 for this micrograph, e. g., a sinuous patch just beyond the 

 right-hand margin a little above the center. Most of this 

 constituent, however, has been destroyed by oxidation. The 

 black patches represent oxidation cavities. They are very 

 numerous and the highly oxidized condition of the specimen 

 was apparent from the crumbly character of the drillings, the 

 friability of the metal, and the nature of the analytical results 

 (total metallics 97.64 per cent, cf. Table I). ISTo direct 

 determination of oxygen was made. 



It seemed unwise to mutilate this unusual object except on 

 one side only. Consequently, a section was not taken through 

 the blade. However, some parts of it were polished as well 

 as possible by manipulating the whole object on the polishing 

 discs. The subsequent examination showed that the blade had 

 been shaped after casting but without sufficiently drastic 

 annealing treatment to remove the casting cores or even the 

 patches of complex. Very fine-grained recrystallization had 

 occurred and prominent deformational characteristics were 



