160 
GEOLOGICAL REPORT—THIRTY-FIFTH PARALLEL. 
18 Fevrier.—Du No. 64 ' au 65'.—On traverse 
une vaste plaine cle sable et nous Campons a 
Fentree d’ un grand canon, qui est entierement 
dans le systeme Cerbat. 
19 Fevrier.—Du No. 55' un No. 66', 8 milles 
—Tout le temps dans un canon dont les haut¬ 
eurs sont couronnees par un trap basaltique, et 
la base est des gres rouge argilleux, puis un 
poudingue rouge, sans marque de stratification. 
On voit, de temps a autres, de larges dykes de 
talcose schiste et de gneiss. La couleur des 
rocbes, en general, est brune rougeatre. Pas 
de diluvium dans le canon. 
20 Fevrier.—Du No. 66' au No. 6*7', 8 
milles —Les quatre premiers milles on est 
dans le meme canon avec gneiss porphyroid 
rouge, couronne par le trap basaltique au som- 
met. A droite le canon s’elargit et l’on a 
de vastes collines de 200 pieds de hauteur 
de - [?] drift et l’on arrive a l’embou- 
clmre du Bill Williams'’ fork dans le grand 
Colorado. 
Au sud le Rio Colorado s’engage dans un 
canon etroit de meme roche rougeatre; au 
nord, ou l’on remonte, la vallee est du drift 
quaternaire, a un endroit on a ce gres rouge 
avec couches de drift et argile redresses de 20° 
et plongeant a l’ouest; c’est le meme tertiaire 
que precedemment. 
21 Fevrier.—Du No. 67' au No. 68'.—Sur 
le diluvium quaternaire pres de la riviere, 
quelques endroits d’argile rouge du tertiaire 
releves et inclinant a l’ouest, angle 20°. A 
trois milles a Pest, on a les montagnes de 
gneiss porpliyroide rouge du Cerbat systeme. 
De Pautre cote de la riviere, Cerbat systeme 
aussi. Hauteur des montagnes de 1,000 a 
1,200 pied. 
22 Fevrier. — Du No. 68' au No. 69', 10 
milles. —On entre au sortir du camp dans des 
montagnes qui viennent butter au rio; ces 
montagnes sont des gres et poudingues rouges 
tertiaire metamorphiques et endurcis par des 
traps basaltiques et amygdaloides, a 7 milles 
le long du Rio Colorado, on a des granites 
serpentineux et des quartz protogenes tres 
beaux. De Pautre cote du rio memes mon- 
February 18.— From Camp No. 124 to No. 
125. '—We crossed a vast plain of sand and en¬ 
camped at the beginning of a great canon 
which is entirely in the Cerbat system. 
February 19.— From Camp No. 125 to No. 
126. —We were all the way in a canon the 
heights of which are surmounted by a basaltic 
trap, the base being of red argillaceous sand¬ 
stone, then a red conglomerate without any 
trace of stratification. We saw, now and then, 
large dykes of gneiss and talcose schists. The 
color of the beds, in general, is reddish-brown. 
No diluvium in the canon. 
February 20.— From Camp No. 126 to No. 
127. (8^ miles.) —For the first four miles we 
travel in the same canon with red porphyroid 
gneiss, surmounted at the summit by red ba¬ 
saltic trap. On the right the canon widens, and 
we found vast hills, two hundred feet in height, 
of-[?] drift. We arrived at the mouth of 
Bill Williams’ fork, in the Great Colorado. 
South of the Colorado, we pass in a nar¬ 
row canon of the same reddish rock. On 
the north, where we ascend the valley is of 
quaternary drift. At one place we found the 
red sandstone, with beds of drift and red clay, 
upraised at an angle of twenty degrees, and 
dipping to the west; it is the same Tertiary 
formation before mentioned. 
February 21.— From Camp No. 127 to No. 
128. —We travelled on the quaternary diluvium 
near to the river, and passed in some places the 
red clays of the Tertiary, upraised and inclin¬ 
ing towards the west at an angle of twenty 
degrees. Three miles eastward we found 
mountains of red porphyritic gneiss of the Cer¬ 
bat system. The Cerbat system also extends on 
the other side of the river. Height of the 
mountains from 1,000 to 1,200 feet. 
February 22.— From Camp No. 128 to No. 
129. (10 miles.) —On leaving camp, we entre 
mountains which abut upon the river. These 
mountains are of metamorphosed Tertiary red 
sandstones and conglomerates, and are hard¬ 
ened by basaltic traps and amygdaloids. Seven 
miles from camp along tbe river, we found 
serpentinoid granite, quartzose, protogine, and 
very fine. On the other side of the river we 
