THE GEOGRAPHICAL RESULTS OF THE ROOSEVELT- 
RONDON EXPEDITION 
By W. L. G. Joerg 
American Geographical Society 
to the excellent one of Africa 
published in the London Geographi- 
cal Journal in 1911 — showing the state 
of our knowledge, a year ago, of the 
. topography of South America, we would 
find right in the heart of the continent a 
blank space as large and as long as 
Nevada. Across the whole length of 
this unknown territory lay the route of 
the Roosevelt-Rondon expedition. Its 
borders were long well known, although 
in some cases accurate surveys had not 
been made until recent years. To the 
northwest lies the Madeira River, one 
of the most important highways of the 
Amazon basin, the authoritative survey 
of which was carried out in 1878 by an 
American naval officer, Commander 
T. O. Selfridge; to the north lies a 
group of three rivers, the Canuma, 
Abacaxis and Maué-asst, whose lower 
courses, which drain into a backwater 
connecting the Madeira and the Amazon, 
have been known since Chandless’ 
survey in 1868; to the east flows the 
Tapajoz, one of the main affluents of the 
Amazon, long known and in 1895-6 
more accurately explored by the French 
traveler Coudreau; and, finally, to the 
southwest the unknown area is bounded 
by the Gy-Parand, which was properly 
mapped only in 1907 on one of Colonel 
Rondon’s previous expeditions. These 
expeditions were undertaken on behalf 
of the Brazilian government to construct 
a telegraph line to the rubber settle- 
ments on the Madeira and resulted in 
the exploration of the whole little-known 
highland region extending from the 
| we could consult a map — similar 
upper Paraguay to the upper Madeira, 
together with the drainage systems of 
both slopes. It was on the occasion of 
the second of these expeditions, in 1909, 
that Colonel Rondon came across the 
headwaters of a river flowing northward. 
To follow it to its mouth was the object 
of the 1914 expedition. It might have 
veered to the left and turned out to be 
nothing but a source-stream of the Gy- 
Parana; or it might have bent eastward 
and developed into a tributary of the 
Juruena, one of the sources of the Tapa- 
joz. It did neither. It flowed almost 
due north and thereby crossed the 
unknown area from end toend. Therein 
lies the importance of the discovery. 
The new river thus turns out to be 
the longest known tributary of the 
Madeira; its length is about 900 miles 
and it extends over seven degrees of 
latitude. Its position permits various 
conjectures as to the hydrography of 
the region. 
To the west, between it and the Gy- 
Parana, the interval seems too small to 
allow a river system of any consider- 
able size to develop; this area is proba- 
bly drained in opposite directions by 
their tributaries. A remark in Colonel 
Roosevelt’s book! would seem to cor- 
roborate this assumption. He tells of 
hearing of one of the rubber-gatherers 
who lost his way while working on the 
Gy-Parana and, after wandering about 
for twenty-eight days, finally came out 
on the Maderainha River, which is a 
1 THROUGH THE BRAZILIAN WILDERNESS. By 
Theodore Roosevelt. Charles Scribner’s Sons, 
New York, 1914. 
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