IOWA ACADEMY OF SCIENCES. 
67 
water for at least 12 miles. In contrast with the sagebrush 
growth of the desert here is a luxuriant vegetation. The 
trees are mainly Juniper and Populus angustifolia and 
P. tremuloides. Sedges are many, and among the flowering 
plants were two species unlike anything found along the 
desert streams, for all of these streams on the south side of 
the river have a similar vegetation: but here is a species 
of orchid growing abundantly , — Spiranthes romanzoffiana; 
the nearest locality in which we found it was Stanley Lake 
in the Sawtooth mountains about 500 miles away. The 
other was a species of gentian, alow, one-flowered plant, 
unlike any other species found and unlike anything 
described in the northwest flora. 
Beyond this basin is what seems to be the latest of these 
flows; it is but little weathered, hard and sharp, just as the 
writhing, twisting, swirling mass cooled, apparently 
unchanged since the eruption. 
Following up the grade of this flow we found a breaking 
in of the surface lava. We descended about 20 feet and 
discovered a series of chambers or caves. They were about 
100 feet long more or less, with a width of 20 feet and an 
arched roof 10 feet in its greatest height, and about 2 feet 
where one communicated with another. 
These caves were doubtless formed in the cooling of the 
lava; as the surface cools first the flowing continues below, 
thus forming these cavities. 
As the surface crust was broken down in several places 
we were able to follow one series for about a quarter of a 
mile. In one chamber which had direct communication 
with the outside, was a floor of ice, which by the light of 
lanterns afforded a unique skating pond. The tempera- 
ture must have been at the freezing point, although it was 
the middle of July and outside the thermometer stood at 
110 Q , in the sun, for there was no shade. Our course in 
these caverns was finally obstructed by a flowing stream 
which utilized these cavities for a bed. 
Beyond this plain, coming down from mountains, are a 
number of lost rivers, so called because they disappear in 
