L30 



Footi and Buell— Peruvian Bronze Axes. 



Dnder a hammer, it broke in pieces. By heating above 500° 

 0. and quenching, however, to retain the /3-crystals, we were 

 able to forge the axe cold without any material difficulty, but 

 it was found necessary to anneal at intervals (hiring the forg- 

 ing, heating each time above 500° C. and quenching. 



Photographs were made showing the microstructure of the 

 original casting from which the new axe was made, before the 

 alloy had been worked or annealed. Fig. 2 shows this struc- 

 ture, which is characteristic of alloys of this type, made up of 

 fern-like or kidney -shaped 'casting crystals.' Figs. 3 and 4 show 

 the structure of the new axe in its finished condition after 

 annealing and forging as described above. Fig. 3 was taken near 

 the center of the axe and shows the crystals with no distortion. 

 Fig. 4 was taken near the edge and shows slight distortion of 

 the crystals due to forging. From a comparison of figs. 2, 3, 

 and 4, it is evident that the structure has been entirely changed 

 by annealing and forging. 



The original axe, No. 1, shows from its shape, and from the 



Fig. 3. 



Fig. 3. 



Fig. 2. Showing casting structure of new axe. 

 Fig. 3. Showing structure on center of finished axe. 

 shown in fie. 2. 



Made from metal 



marks on it, that it has been forged. The original shape of 

 the casting cannot be told, but there can be no doubt that the 

 shape has been materially changed by the forging. Figs. 5 

 and 6 show the micro-structure of this axe. It is similar in 

 type to that shown in tigs. 3 and 4 and entirely different from 

 that in fig. 2. The size of the crystals is different. That, 

 however, is controlled by the temperature before quenching. 

 The size of crystals produced by annealing is usually a 



