132 Foots and Buell — Peruvian Bronze Axes. 



Fig. 8. 



Fig. 8. Showing crystals on axe No. 3, a short distance from edge on 

 cross section. 



We were nnable to obtain an etching of axe No. 2. Appar- 

 ently the silver in it gave trouble by dissolving in all the 

 etching solutions which we tried and reprecipitating on the 

 surface, leaving a dark deposit which prevented the micro- 

 structure from being observed. Figs. 7 and 8 show the micro- 

 strncture of the fragment of axe No. 3. Foth views were 

 taken on the broken section. The fine crystals occurred close 

 to the edge at the extreme left as shown in tig. 1 and the 

 coarse crystals occurred nearer the center. The axe was 

 therefore very unevenly heated, either in the original anneal- 

 ing or at some time afterward. 



None of the old axes are very hard. The following table 

 gives the results of the scleroscope tests : 



Edge 



Center 



New axe 



No. 1 



No. 2 



No. 



36 



26 



18 



1! 



34 



24 



20 





The hardness was taken with the Shore scleroscope and 

 it varies somewhat with the percentage of tin as would be 

 expected, but shows nothing at all unusual. In fact, the hard- 

 ness of the old axes is considerably less than that of the new 

 axe, which is probably due. to coarser structure as well as to 

 composition. The values given in the table are expressed in 

 empirical units and merely give comparative values among 

 themselves. For the sake of comparing the hardness of the 

 axes with that of another metal, it may be well to add that a 

 piece of cast brass has a hardness on the same scale of 11 or 12 

 units. 



Chemical Laboratories of the Sheffield Scientific School 



and of the Winchester Repeating Arms Co. 



New Haven, Conn., May, 1912. 



