/. Bowman — A Buried Wall at Cuzco. 



501 



slope of the terrace accumulates sand and gravel on the upper 

 side of the wall. It should be noted, however, that the buried 

 wall is faced not only on its upper, but also on its lower side 

 by stratified gravels at least 15, and possibly 40 or 50 feet 

 thick. Irrigation can not account for the material since it 

 would here imply the up-hill flow of water. The difficulty 

 disappears if we apply the hypothesis of burial by aggradation 

 from above, and have the material move down the slope of 

 the alluvium (fig. 2). 



Fig. 4. 



Fig. 4. The alluvial fringe in which lies the buried wall. The waste- 

 cloaked rock slope of fig. 2 is on the right ; the alluvium begins on the line 

 marking the change of gradient. The Cuzco basin and the western border 

 of the city of Cuzco in the middle distance. 



It is indeed the slope of the alluvium that has the most strik- 

 ing relation to the buried wall. It is a smooth slope with an 

 entirely normal appearance. It breaks distinctly with the 

 thinly-cloaked rock slope from which its material was chiefly de- 

 rived ; and when the plane of the slope is continued downward 

 it is seen to correspond in level with the slope on the opposite 

 side of the ravine. Furthermore, the lower section of the 

 slope has a flatter gradient than the section above in the man- 

 ner of alluvial material accumidated under natural conditions. 

 Beyond the wall (right, fig. 2) the natural alluvial slope 

 becomes broken, in some places almost at the wall, in others 

 some yards away. The irregularities are caused by artificial 

 excavation, by breaks in the wall, which have permitted the 



