66 
IOWA ACADEMY OF SCIENCES. 
In the eastern part of the Snake river desert is a portion 
designated on the map, Rolling Plains, Sand and Lava. 
The sand is a very great obstruction. The plains are more 
or less sandy until the sand-hills or dunes are reached. 
These form the most conspicuous feature of this region. 
At a distance of about 60 miles they have the appearance 
of a low mountain range, peculiar in the fact that their 
color is strikingly white against the darkness of the 
farther mountains. On closer inspection they are some- 
what darker, the sand being composed of quartz crystals 
mixed with particles of lava. The range is estimated to 
be 30 miles long and from 3 to 8 miles wide. Some of the 
dunes reach a height of 300 feet; on the windward side 
they are gently sloping and ripple-marked by the wind, 
while the other side is perpendicular. These large dunes 
stand entirely alone and travel independently — the rate of 
travel varying with the velocity of the wind. They have 
been known to advance one foot per day. They are 
approaching the Snake river, and whether they are strong 
enough to cross the stream or if their sand shall be washed 
away by the swift current will be known by the future. I 
have given these only a brief mention because of their con- 
spicuousness, and because of their obstruction to other 
investigations. 
Starting from Saint Anthony and traveling in a north- 
erly direction, after the first mile or so the lava plains are 
exceedingly rough and bare except for the sand and the 
sagebrush which is more or less scanty. In this course for 
about 12 miles it seems to be apparent that there were 
several lava flows, for one flow seems to overlap another, 
the successive margins marked by an abrupt cliff or shelf; 
each succeeding- terrace being marked by less weathering 
and hence by less vegetation. 
In this distance five of these shelves were counted, then 
suddenly appearing in the midst of this lava w T aste, in a 
slight depression or basin, is a fertile tract very springy 
and marshy, covering probably 2 or 3 sections, which is 
entirely surrounded by the lava desert with no sign of 
