CHAPTER XXV.
Substitute for Fuel on the Prairies .-- Fossil Trees .-- Fierceness of the Buffaloes When in Heat .-- Three Hunters Missing .-- Signal Fires and Smokes .-- Uneasiness Concerning the Lost Men .-- A Plan to Forestall a Rogue .-- New Arrangement With Rose .-- Return of the Wanderers.
THE plains over which the travellers were journeying continued to be destitute of trees or even shrubs; insomuch that they had to use the dung of the buffalo for fuel, as the Arabs of the desert use that of the camel.

This substitute for fuel is universal among the Indians of these upper prairies, and is said to make a fire equal to that of turf.

If a few chips are added, it throws out a cheerful and kindly blaze.
These plains, however, had not always been equally destitute of wood, as was evident from the trunks of the trees which the travellers repeatedly met with, some still standing, others lying about in broken fragments, but all in a fossil state, having flourished in times long past.

In these singular remains, the original grain of the wood was still so distinct that they could be ascertained to be the ruins of oak trees.
Several pieces of the fossil wood were selected by the men to serve as whetstones.
In this part of the journey there was no lack of provisions, for the prairies were covered with immense herds of buffalo.

These, in general, are animals of peaceful demeanor, grazing quietly like domestic cattle; but this was the season when they are in heat, and when the bulls are usually fierce and pugnacious.