/. Bowman — A Buried Wall at Cuzco. 505 



gradient of the surface. The buried channel and wall would 

 "then have flatter gradients than the surface channel and slope. 

 Later excavation, either artificial or natural, would expose the 

 buried wall and make apparent the discordance between two 

 sets of things made at two different times under different con- 

 ditions. 



This line of reasoning is further supported by the fact that 

 the stratified gravels abut sharply against the wall on both 

 sides and even overtop it in an unbroken series. The wall 

 was not built into alluvial deposits, but was covered by them 

 after it was built. Even if a wall were built squarely against 

 a cleanly cut gravel bank, it could not fit the face of the bank 

 so closely but that percolating water would rearrange the 

 material and leave, between the undisturbed stratified gravel 

 and the wall, a zone of unstratified fill like that so often seen 

 on the outside of an old house foundation in process of re-ex- 

 cavation. The difference in gradient is interpreted, then, as a 

 condition which might be due to the building of a wall in the 

 bottom or along the side of a ravine, were it not that the 

 gravels abut sharply against both sides of the wall without a 

 facing of unstratified material. 



Among the facts that point to burial of the wall, a second 

 one, the material of the alluvium, may now be considered. 

 The wall rests upon a rather pure sand, distinctly not a gravel, 

 as determined by excavation. Coarse gravels, however, con- 

 stitute the alluvium that banks against the wall and appear in 

 the section on the side of the ravine opposite the wall. The 

 top of the section consists in general of finer material. In this 

 succession of coarse and fine we have a condition in itself 

 indicative of a change from degradation to aggradation and 

 back again to degradation. The wall rests upon fine material 

 accumulated at a time when wash from surrounding highlands 

 w T as feeble and transportation slow ; the coarser material above 

 it represents the streams in full vigor loaded with detritus 

 both coarse and fine which they accumulated upon a former 

 alluvial slope ; the finer material at the top represents the 

 deposits of waning streams. 



Quite apart from the repeated testimony of residents that 

 the present channel in which the wall stands was opened in 

 recent years, and therefore that the wall was not used as a 

 retaining dike for terrace front or irrigating stream, is the evi- 

 dence afforded by the alternating ash and sand beds in the 

 upper few feet of the alluvial fringe. Near the lower end of 

 the map, BM U , fig. 1, the ravine cuts through a section of 

 most peculiar composition. On the right hand side (facing 

 down the ravine) are interstratified ashes, pottery, and bone 

 fragments, together with pieces of charred wood, corn, and 



