The Lake Systems of Southern Patagonia. — Hatcher. 167 
Detrital Deposits. The detrital deposits of the Pleistocene, 
or Quaternary, are developed on an enormous scale in southern 
Arizona. They everywhere skirt the mountains in the form of 
extended slopes often twenty miles or more in length which 
arrest the eye by their wonderful regularity of outline truly 
represented in a photograph or picture by a straight line in- 
clined two or three degrees to the horizon. 
THE LAKE SYSTEMS OF SOUTHERN PATAGONIA. 
By J. B. Hatcher, Carnegie Museum, Pittsburgh, Pa. 
Plate XVI. 
Until recently, the interior of Patagonia has remained prac- 
tically an unknown country. A few of the earlier travelers had, 
it is true, penetrated into the interior, but for the most part they 
followed one of two routes. Some chose the Santa Cruz river, 
which, discharging into the Atlantic at about the fiftieth paral- 
lel of south latitude, forms an unbroken waterway, for vessels 
of light draft, from the sea to lake Argentino at the base of the 
Andes, 150 miles to the westward. Others, starting from the 
same point, selected a more northerly route, and after leaving 
the mouth of the Santa Cruz river, followed the old Indian trail 
that, for centuries, has formed the highway of communication 
between the southern Tehuelches and the Araucanians and 
other Indian tribes inhabiting the country watered by the 
Chubut, Negro, and Colorado rivers, far to the northward. 
This trail, after leaving the Santa Cruz river near its mouth, 
assumes a northwesterly direction, and taking advantage of the 
valley of the Rio Chico which has cut a practical highway 
through the broad lava beds that cover most of the central 
plains of southern Patagonia, it ascends this stream to a point 
some forty miles distant from the eastern base of the Andes. 
At this place a tributary valley enters the main river valley 
from the north. This valley connects with other similar lateral 
valleys tributary to the drainage systems lying to the northward 
and thus there is formed a continuous highway extending par- 
allel with the base of the Andes from the Rio Chico to the Rio 
Negro. 
•From the Bulletin of the Geographical Society of Pbilaclelphia, \o\. \\, 
No. 6. 
