re on the north side of the basin. Waste material from its
slopes is causing the rapid growth of a great gravel fan north of the
village of San Geronimo. Professor Gregory noticed that the streams
traversing the fan are even now engaged in burying ancient fields by
"transporting gravel from the head of the fan to its lower margin,"
and that the lower end of the Cuzco Basin, where the Huatanay, hemmed
in between the Angostura Narrows, cannot carry away the sediment as
fast as it is brought down by its tributaries, is being choked up. If
old Saylla represents a fortress set here to defend Cuzco against old
Oropesa, it might very naturally have been abandoned when the rule
of the Incas finally spread far over the Andes. On the other hand,
it seems more likely that the people who built Saylla were farmers
and that when the lower Cuzco Basin was filled up by aggradation,
due to increased erosion, they abandoned this site for one nearer the
arable lands. One may imagine the dismay with which the agricultural
residents of these ancient houses saw their beautiful fields at the
bottom of the hill, covered in a few days, or even hours, by enormous
quantities of coarse gravel brought down from the steep slopes of Picol
after some driving rainstorm. It may have been some such catastrophe
that led them to take up their residence elsewhere. As a matter of
fact we do not know when it was abandoned. Further investigation
might point to its having been deserted when the Spanish village of
San Geronimo was founded. However, I believe students of agriculture
will agree with me that deforestation, increased erosion, and aggrading
gravel banks probably drove the folk out of Saylla.

The southern rim of the Cuzco Basin is broken by no very striking
peaks, although Huanacaurai (13,427 ft.), the highest point, is
connected in Inca tradition with some of the principal festivals
and religious celebrations. The north side of the Huatanay Valley is
much more irregular, ranging from Ttica Ttica pass (12,000 ft.) to
Mt. Pachatucsa (15,915 ft.), whose five little peaks are frequently
snow-clad. There is no permanent snow either here or elsewhere in
the Huatanay Valley.

The people of the Cuzco Basin are very short of fuel. There is no
native coal. What the railroad uses comes from Australia. Firewood is
scarce. The ancient forests disappeared long ago. The only trees in
sight are a few willows or poplars from Europe and one or two groves of
eucalyp