GEOLOGICAL REPORT-THIRTY-FIFTH PARALLEL. 
162 
reconvert par un trap phonolitique, noiratre, 
brilliant, tout-a-fait basaltique. Pas d’erra- 
tique. 
4 Mars.—Du No. 7G' an No. 77'.—On tra¬ 
verse la seconde chaine qui est partont dn trap; 
pnison a devantsoi nn vaste plateau, qni s’etend 
jusqu’ a la troisieme chaine, le plateau de roche 
eruptive, decomposee et reconvert en plusieurs 
endroits d’un calcaire brechiforme, blanchatre 
horizontal et Tertiaire. Hauteur du plateau, 
4,500 pieds. 
5 Mars.—Du No. 77' au No. 78'.—On vient 
de traverser la plaine ou. il y a du calcaire, 
et l’on entre dans la troisieme chaine, formee de 
granite ampliibolique tres dur ; et l’on voit a 
distance du trap repandu au sommet des mon- 
tagnes. 
7 Mars.—Du No. 78' au No. 79', 20 milles.— 
On traverse la troisieme chaine, qui a 5 ou 6 
milles de long, tout de granite a hornblende, 
tres-dur, excepte au nord du Camp 78' oii il 
y a une roche blanchatre dioritique [?] on entre 
dans un nouveau plateau incline, granitique 
et Ton vient camper sur ce meme granite a 
hornblende au qoied de la quatrieme chaine. 
8 Mars. — DuNo. 79' auNo. 80', troismilles .— 
On traverse la quatrieme chaine, qui est moins 
elevee que la precedents, mais plus longue, elle 
est formee pour 12 milles de granite quartzi- 
fere. A 10 milles de distance au nord du 
sentier on voit sept on huit petits cones 
volcaniques ranges est ouest. On arrive au 
sommet des coles de drift, tres escarpees. Ce 
drift a 800 pieds d’ epaisseur, forme de gros 
blocs tres-peu roules, avec sables. On arrive, 
a 12 milles a droite, a une grande montagne 
de trap greenstone metamorphique ; cela Unit 
la quatrieme chaine ; on a pour 15 milles les 
sables modernes du Rio Mojave, et un lac sec 
avec efflorescence alumineuse et salee. L’ eau 
salee se trouve part-out a £ pied de profond. 
J ai vu aujourd’ hui jusqu a la Sierra Nevada, 
et il y a 9 ou 10 chaines nord sud, paralleles 
entre la Colorado et la Nevada, avec quelques 
petils pates de montagnes entre quelque cones. 
morphic conglomerate covered by black and 
shining phonolitic trap ; also basaltic. No er¬ 
ratics. 
March 4.— From Camp No. 137 to Camp No. 
138. —We crossed over the second chain and 
trap-rock was everywhere visible; we then 
saw before us a vast plateau which extended 
as far as the third chain. This plateau of de¬ 
composed eruptive rocks is covered in several 
places with a whitish limestone which is brec- 
ciated, horizontal and Tertiary. Elevation of 
the plateau 4,500 feet. 
March 5.— From Camp No. 138 to Camp No. 
139. —We arrived at the other side of the 
plain, where there is limestone, and entered 
the third chain, formed of very hard amphi¬ 
bolic granite, and we saw in the distance 
trap-rock spread out on the summit of the 
; mountains. 
March 7.— From Camp No. 140 to Camp No. 
141, (20 miles.) —We crossed the third chain, 
which is five or six miles wide, and composed 
of a very hard hornblendic granite, except at 
the north of Camp No. 140, where there is a 
whitish dioritic? rock. We reached another 
inclined plain of granitic rocks, and we en¬ 
camped on the same hornblendic granite at 
the foot of the fourth chain. 
March 8.— From Camp No. 141 to Camp 
No. 142, (31 miles.) —We crossed the fourth 
chain, which is less elevated than the pre¬ 
ceding, but longer; for twelve miles it is 
formed of quartziferous granite. Ten miles 
north of the pass we saw seven or eight small 
volcanic cones of a red color ; direction east 
and west. We reached the summit of steep 
banks of drift. This drift is 800 feet thick, 
and formed of large blocks, but little rolled, 
and sands. At the distance of twelve miles, 
on the right, we reached a great mountain of 
trap and greenstone, metamorpliic, and which 
ends the fourth chain. We followed for fifteen 
miles the recent sands of the Rio Mojave, and 
a dry lake covered with a salty and aluminous 
i efflorescence. Salt water is everywhere found 
at the depth of six inches. I have seen to-day 
as far as the Sierra Nevada, and there are nine 
or ten north and south chains running parallel 
between the Colorado and Sierra Nevada, with 
some ‘ ‘ pates de montagnes’ ’ between some cones. 
