of Bronzes from Machu Piccliu, Peru. 527 



tion of the anneal. Fortunately, careful study of the recrys- 

 tallization phenomena in a particular group of alloys, such as 

 the present group of alpha-bronzes (see discussion of constitu- 

 tion, p. 540), leads to certain associations and generalizations 

 so that the treatment resulting in a given structure may 

 frequently be specified without the too free admission of bewil- 

 dering assumptions and conditional premises. Certain short- 

 comings must, however, be admitted. For example, a ductile 

 object may be lengthened at will by intensive rolling, drawing, 

 or hammering, if an adequate number of intermediate soften- 

 ings, or annealing, operations are conducted. The final struc- 

 ture and physical properties are determined by the last 

 co-ordinated draft and anneal unless unusually light mechanical 

 or annealing treatment has prevailed. !No knowledge of pre- 

 ceding operations can ordinarily be derived from the structural 

 characteristics at this point. If the duration of the last anneal 

 is approximately known, the temperature region of annealing 

 may be estimated from the mean grain size. Some distinctions 

 can be made without regarding the time factor, e. g., an anneal 

 at bright red heat can be distinguished from one at nascent 

 red, since the coarse grain produced in a very few minutes at 

 the higher temperatures is not much affected by longer exposure 

 and cannot be duplicated by even a very prolonged anneal at the 

 lower temperature. It has thus been possible to fairly esti- 

 mate the temperature which must have been reached in the 

 finishing anneal of some of these old bronzes. 



While, in completely recrystallized structures, the grain 

 characteristics give no indication of the total extension of the 

 piece or the number of stages in the process, partially recrys- 

 tallized structures, in which traces of the cast condition are 

 apparent, indicate that the finished piece corresponds closely 

 in form to the original castings. Thus, a number of the 

 bronzes examined were obviously cast in the rough and wrought 

 into shape, the process requiring a moderate amount of work 

 and a limited number of annealing operations; perhaps only 

 one. 



5. Drastic treatment whereby the object, by successive 

 drafts and anneals, suffers manifold extension in one direction 

 or another may sometimes be recognized by characteristic 

 migrations of insoluble impurities which have remained sensibly 

 unaffected during the heat treatment. Such evidence is purely 

 qualitative, since the extension of individual units within the 

 moving mass is not proportional to the extension of the piece 



