522 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



the old Indian civilizations, knowledge of which had been kept alive 

 through the ages by the untiring efforts of a handful of priests and 

 scholars, chiefly Mexican, but including some Americans and Euro- 

 peans. 



These men had interpreted and preserved the few first-hand native 

 records that had survived the wholesale destructions of documents 

 and religious paraphernalia. They had also collected and observed 

 the material traces of native culture dug up by farmers and treasure 

 hunters and had tried to identify the makers of these objects and the 

 builders of these temples by interpretation of the native annals at 

 their disposal. It became evident, as time went on, that there was 

 vastly more material in the ground than could be accounted for by 

 the tribes mentioned in the historical records. 



Thus in the beginning of the twentieth century, a subsidiary branch 

 of history began to grow up, field archeology, which had for its goal 

 the study of the Indian material culture, its history and development, 

 and its interpretation in terms of human history. One of the chief 

 aims of this branch of research was to try to establish the relative age 

 of the different monuments and cultures. Fragmentary pottery was 

 of the greatest aid in attaining this end. Forms and decoration 

 changed gradually with the years, and each tribe or locality had its 

 own individual expression. By cutting into ancient refuse heaps, 

 where the material at the bottom was necessarily laid down at an 

 earlier date than at the top, and by carefully studying the differences 

 in shape, texture, and decoration of the fragments of pottery found, 

 it was possible to discern the relative age of several ceramic groups. 

 Later, by finding pottery associated with a building, the relative age 

 of that structure could be determined. Furthermore, in Central 

 America, it is quite common to discover that buildings are success- 

 ively enlarged by filling in and adding to a previous construction, so 

 that the stratigraphical process can be applied to architecture as 

 well as to ceramics. 



While such stratigraphical sequences have been established for 

 various parts of Mexico and Central America, the Valley of Mexico 

 is the first where the archeological record is detailed enough to be 

 compared to the historical and where the two lines of research com- 

 plement and check each other. Let us examine this relationship, 

 which is one of the primary ends of archeological research. 



The documentary evidence from the Valley of Mexico consists of 

 two main types. First there were the records kept by the Aztecs 

 and. their neighbors, a few of which escaped the wholesale destruc- 

 tions ordered by the Spaniards. These consisted of a type of picture 

 writing, not unlike a rebus, in which the picture of an object could 

 represent, beside the object itself, the same sound with another 

 meaning or as a syllable in another word. Personages and tribes were 



