of Bronzes from Machu Picchu, Peru. 597 



central portion, and then bent around into shape. The set of 

 the aperture indicates that it was punched rather than drilled. 

 The metal shows a finer recrystallized structure and more 

 prominent cores than were encountered in the case of the 

 partially completed specimen. It, therefore, received less 

 drastic annealing treatment. Its structural characteristics are 

 intermediate between those shown in fig. 49 and fig. 91, more 

 closely approximating the latter. Such an effect would be 

 produced by annealing for a few minutes (5-10) at 700°, or 

 by just allowing the object to reach a temperature some 50° 

 higher. 



Object No. 20 (cf. Table I). 



This object, which weighs over two pounds, is the most mas- 

 sive piece of the entire collection. As may be seen in fig. 28, 

 it represents the lower portion of what may be conveniently 

 called a crowbar. Scleroscopic tests on smooth-filed portions 

 of the surface show that the metal was finished hard, i. e., 

 the hardness numbers vary between 18 and 25. The bar was 

 used in a tensile test which gave an elongation of 6 per cent 

 in 2 inches and an ultimate strength of 27,800 pounds per 

 square inch. Worked bronze of this composition, when 

 hardened so as to possess very little ductility, should show far 

 greater strength than was obtained in this case. The present 

 combination of ductility and strength indicates metal of very 

 poor quality. A polished and etched section near the fracture 

 revealed a multitude of large and small holes with blackened, 

 or oxidized surfaces. These predominate near the center of 

 the cross section. Nearer the surface the holes have been closed 

 in working the metal but without removing the source of 

 weakness, since no true welding has occurred. The metal 

 appears to have oxidized as a result of some initial porosity 

 and much annealing treatment. 



Object No. 21 (cf. Table I). 



The small piece of metal illustrated in fig. 29 is one of 

 several small shapes, bars, rods, etc., which probably constituted 

 material intended for subsequent shaping into objects of some 

 particular significance. This piece has been worked and 

 annealed to a condition of complete homogeneity. The absence 

 of deformational characteristics and the observed hardness 

 number of 9-10 show that it is now soft and well adapted to 

 further mechanical treatment. 



Sheffield Scientific School of Yale University, 

 New Haven, Conn., June 20, 1915. 



