Between these two rivers and extending across the Paraguay River into Paraguay lies what is known as the Gran Chaco. This is a broad plain, alternating with forest, which includes thousands of square miles of territory. It is the least known of Argentine territory, because of the difficulties of travel, and also because of the fact that wild and savage Indians who lead a nomadic existence are still to be found in certain sections. It was a mysterious and strange country to the early explorers. Into this wilderness the natives fled, and both fancy and imagination peopled it with all manner of strange wild beasts. The territorial boundaries were never definitely settled, until President Hayes, acting as arbitrator, fixed the boundaries between Paraguay and Argentina. These vast leagues are now divided into two territories, Formosa and Chaco. The former is almost as large as Ohio and the latter equals Illinois. In the two territories the reported population is about one person to each five square miles. There are many curious phenomena in the Chaco. The edges between plain and woodland are as clearly cut and as straight as if a surveyor had done the work. In fact the line of demarkation is drawn with remarkable exactitude. On one side will be a forest, and on the other the smooth plain stretches out with not a tree upon it to break the severity of the contrast. In other places there will be only palm trees, with not a single specimen of another species for variety. It is a land of strange watercourses. Broad streams that have ploughed all the way from the Andes in the full light of day burrow beneath the ground in the Chaco and continue their course underground. During heavy rainfalls it is claimed that small fish descend from the clouds. Fish eight or ten inches in length will be found in pools after showers, where there had been no water, and the ground had been in a parched condition for months. Do they lie imbedded in the earth like frogs? Are these fish amphibious? These questions have not yet been answered. It is a fact that there are many odd phases of nature in this little known section of Argentina; the same character is found in a goodly part of Paraguay, and it even extends up into Brazil. [Illustration: A FOREST IN THE GRAN CHACO]