A Trip to Fremont River 311 
and on the 25th of May (1872) Thompson started at the head 
of the party to try to explore a way in to the mouth of the 
Dirty Devil, at the same time investigating the country lying 
in between and examining the Unknown or Dirty Devil 
Mountains which had been seen from the river, just west of 
the course of the Dirty Devil River, now named Fremont 
River. We went west to a ranch called Johnson after the 
owner, thence north-westerly, passing the little Mormon 
settlement of Clarkson, and then struck out into the wilder¬ 
ness. Keeping a north-westerly course we crossed the upper 
Lake on the Aquarius Plateau. 
Photograph by J. K. Hillers, U. S. Colo. Riv. Exp. 
waters of the Paria and made our way to the head of a stream 
flowing through what was called Potato Valley, and which the 
party of the previous year had followed down, endeavouring 
to find a trail by which to bring rations to us, under the im¬ 
pression that it was the head of the Dirty Devil. We also 
turned our course down it with the same idea. We had taken 
with us a Pai Ute guide whom we called Tom, but as we ad¬ 
vanced into this region so far from his range, Tom got nervous 
and wanted to go back, and we saw him no more till our re¬ 
turn, Six years before a Mormon reconnoitring party had 
