of Bronzes from Machu Picchu, Peru. 581 



short exposure at a materially higher temperature would have 

 produced a distinctly coarser grain. It is also probable that 

 the temperature of this portion was not greatly inferior to 

 700°, since a drop of 50 or 75° would necessitate a very lengthy 

 period of annealing in order to produce the present character- 

 istics. It is the writer's opinion that, in the annealing of this 

 pin, a moderate red heat was developed near the point with 

 gradual fall to black heat at the head. 



Deformational characteristics abound all over the object. 

 Fig. IS has already been cited in this connection (p. 578). 

 This is an interesting photo-micrograph as it shows (1) a 

 primary zonal structure, e. g., dark-etching centers as in the 

 lower left hand corner, (2) portions of the casting grains altered 

 by severe deformation, and (3) small but clearly distinguish- 

 able recrystallized grains. In fig. 47, magnification 12 X> the 

 field of view is carried from the lower part of the head-section 

 (vicinity of fig. 48) as far as the massive part of the head. 

 It reveals a casting structure of normal appearance. Altera 1 

 tion of the order shown in fig. 48 is not indicated under this 

 low power. Exploration of the upper part of the head-section 

 under high power has shown that the star-branches and the 

 knob at the top preserve the general shape of the original cast- 

 ing but were brought to a smooth finish by hammering or some 

 deeper-seated process than that of simple abrasion. The sur- 

 face characteristics of the shank were reproduced in the 

 laboratory by hammering on the anvil with a broad-faced 

 hammer. 



Object No. k (cf. Table I). 



This is one of the several very nearly spherical objects 

 included in the collection, all of them provided with a point 

 of attachment in the shape of a pin sunk into a hemispherical 

 cavity. They may have been used as plumb-bobs, sounding, 

 or fishing weights, etc. This specimen is illustrated in fig. 12, 

 and a diagram of the section examined is given in fig. 50. 

 The cut along this plane traversed the pin centrally from end 

 to end and divided the object symmetrically into two parts. 



The finer structural detail of the object is of secondary 

 importance. It is particularly desirable to illustrate the two 

 types of crystallization encountered, one in the body of the 

 object and the other in the pin, as well as the form of transi- 

 tion from one to the other. This is best effected through the 

 medium of photo-micrographs at low power prepared after a 



