8oo The American Naturalist. [September, 
comes a large river ; a few miles below the San Francisco joins it, and 
from this point to its mouth, 900 miles, it receives no tributary of any 
importance. All changes in the course of the Bermejo and of the 
middle and lower sections of the Pilcomayo exhibit a tendency to 
swerve to the eastward. The most important alteration of recent 
years was that of the Bermejo, which in 1869-70 became deflected at 
23° 40' S. and 63° 35' W. from its ancient bed, and did not find a 
new one until 1872, when the main body of waters took a parallel 
course to the north and east of the old bed, forming an island 200 
miles long. The Gran Chaco is no desert, but a rich alluvial lowland, 
fitted for colonization, which is hindered by the want of knowledge of 
the rivers and their shiftings. The forests yield many valuable woods, 
among them the tatane {Portiera hygrometricd), the palo rosa, the 
Cesalpinia melanocarpa) the urendey, rurupay, and quebracho, three 
species of algarroba or Prosopis, and the palo santo or lignura-vitse. 
There are also many native fruits of good quality. The Austral Chaco 
has been developed along the banks of the Parana, where many pros- 
perous colonies exist, and there is a successful colony about 140 miles 
from the mouth of the Bermejo. There are not more than 30,000 
Indians in the entire Chaco. In the discussion which followed Captain 
Page's description of the Gran Chaco, Colonel Church said that the 
rainfall of the Chaco, or forest region, was from November to May, 
and was a downpour of som^ eighty inches. The rainy season of the 
Pampas was not at the same time. During the rains there was at the 
head-waters of the Bermejo a lagoon forty leagues across. The Pilco- 
mayo, at 180 leagues from its mouth, filtered through a sandy swamp 
100 miles across, and its bed above this was a mass of sandbanks, falls, 
rapids and snags. The Gran Chaco was in flood-time almost a lake 
region, and the upper Paraguay became an inland ocean. This flood 
district extended northward to the falls of the Madeira, 11° S., and 
northwest 
across the Beni almc 
)st to Peru. In 1 
:he Be 
ni there ^ 
.vasa 
lake of 2( 
3, 000 square miles, t 
wo to seven feet 
deep. 
It had 
been 
calculated 
that the Bermejo' a 
nnually delivered 
the Paraguay 
6,500,000 
cubic yards of detrit 
:us. Under these 
circumstances, 
navi- 
gation of 
these rivers seemed air 
nost impossible. 
The Selkirk Range Glaciers.— An interesti 
ng account of e 
xplo- 
rations in the glacier regions of the Selkirk range, west of the Rocky 
mountain water-divide, on the Canadian and Pacific railway, is given 
by the Rev. W. S. Green in the March issue of the Royal Geo- 
graphical Society's proceedings. Mammalian life seems to be particu- 
larly abundant in this range, and the strange habit of the Sewellel for 
