BASALTS OF THE UINKARET. 
105 
“linear arrangement” is often seen. From three to seven or eight cones 
may be found in rows, as if they were so many vents occurring along the 
course of a single fissure. Very many, however, seem too isolated in this 
respect. For aught we know, the fissure may be there, but only one vent 
is situated upon it. It may be remarked here that no evidence has been 
found on the Uinkaret that these vents have any association wdth fissures, 
beyond the mere fact that the linear arrangement is in quite a number of 
cases well marked. For example, on the Kanab Plateau, three or four miles 
east of the Toroweap, is a line of craters, seven in all, occurring at intervals 
of two or three miles. Each has around its base a few small coulees of 
basalt, but the country between them is in greatest part free from lava. 
There is no trace of a fault or fissure visible there. A fault of any notable 
magnitude could not escape detection, and a fissure, if it exists there, has 
been wholly concealed The same is true of the other lines of craters. 
Although the intervals between them are frequently free from lava, and the 
edges of the Permian beds well exposed in many of the shallow vales, no 
trace of such a fracture has yet been seen. Still, the fissures may be quite 
small — only a yard or two in width — and they may have been covered so 
effectually by alluvium that they have escaped observation. The basalts 
here show no tendency to seek the great fault planes as favorite places from 
which to erupt. I am inclined (with some reserve) to remark that they 
rather avoid such places, ot’ resort to them less frequently than to others. 
There are very few cases where the crater seems to be very nearly or ex- 
actly upon the line of a great fault. Vulcan’s Throne, at the foot of the 
Toroweap, is such an one, and four or five other instances have been noted. 
The strongest feature of such occurrences, however, is their paucity. If 
there be any specially favored locus of eruption, with reference to a great 
fault, I should say that it may be found along the upthrow of the fault, and 
from a mile and a half to four or five miles from the plane or line of dislo- 
cation. While exceptional cases are found, they are very uncommon. 
The heavy lava caps which form the summits of Trumbull and Logan, 
and the platform on which the crater Emma stands, have nothing in common 
with the craters just mentioned. These basalts did not come from such 
craters, but are much older. The vents from which they issued have been 
