' THE GlIANI) GA5JON DISTRICT. 
At dawn we moved onward, reaching soon the summit of a hill which 
descends two or three hundred feet to a broad flat depression called the 
Wonsits Plain. It is a. very barren and smooth expanse, dotted with a few 
moldering buttes of Upper Carboniferous rocks, now wasted to their foun- 
dations. The plain is about seven miles in width, and on the further side 
rises a low mesa of great extent capped with basalt. It is the Uinkaret. 
Beyond the nearer throng of basaltic cones Mount Trumbull rises with a 
striking aspect dominating strongly the entire western landscape. The 
smaller cones are now seen to be very numerous, and all of them are ap- 
parently perfect in form, as if time had wrought no great ravage among 
them. The lapilli and peperino, with which they are covered, have become 
dull red by the oxidation of the iron, and this peculiar color is easily recog- 
nized though the cones are still far away. Just before reaching the basaltic 
mesa we must make our choice between two routes to the Toroweap, one 
direct, the other very circuitous. No spring is to be found until we reach 
the further side of Mount Trumbull, but we know of a large water-pocket 
on this side, which has never been known to dry up. The spring water is 
sure to be good, but the water in the pocket will depend for its quality upon 
the length of time which has passed since the last heavy rain. Let us here 
choose the shorter one, and go to the water-pocket. 
Ascending the mesa, which rises abruptly about 200 feet above the 
Wonsits Plain, we find ourselves at once upon the basalt. The ground is 
paved with cinders and fragments half buried in soil, the debris of decaying 
lava sheets. These sheets are rarely of any great thickness, seldom ex- 
ceeding 30 or 40 feet, and often much less, and none of the individual erup- 
tions of lava seem to have covered any very great expanse. Probably the 
area covered by the largest would be less than a square mile. They show 
no perceptible differences in composition or texture, and all are basalts of 
the most typical variety— very black and ferruginous in the unweathered 
specimens and speckled with abundant olivine. At the time of eruption 
they appear to have been in a state of perfect liquidity, spreading out very 
thin and flowing rapidlj^ and with ease. In none of them has erosion 
wrought much havoc, though here and there some local destruction has 
been effected, most conspicuously upon the edges of the principal mesa 
