GEOLOGICAL REPORT. 



of gray, yellowish, reddish, and white colors, which form high escarpments 

 southwest foot of the island mountain north of Clay Creek, Mount I.owry. 



The strata comprising this mountain and the one north from there, near 1 

 Creek, are mostly limestones of Ught-gray color, subcrvstalline and very co 

 Only a few imperfect fossils were noticed in them, some troth Unnn univalves, an 

 coralline forms, which, according to Mr. Meek, appear to be similar to Lower S 

 species from the Western States. The dip of these strata also seems to indica 

 they occupy a lower geological horizon than those of Swallow Canon, and ho 

 deuces, although not conclusive in themselves, lead me to consider these strata i\ 

 probably Silurian. 



Crossing Pah-hun-nu-pe Valley on the northern road, we find on its we 

 cliffs of a light-gray, granular, crystalline, magnesian limestone, an agglomera 

 small rhomboidal crystals of dolomite, altogether presenting the appearance of 

 of the Lower Silurian magnesian limestones of Missouri, especially the third i 

 sian limestone of Professor Swallow. This series is several hundred feet thic 

 succeeded by lower strata of a similar character, but more finely crystalline an< 

 crystalline, like other varieties of the third magnesian limestone. They are am 

 by several hundred feet of coarse sandstones and siliceous conglomerates, which 

 also correspond to a sandstone in the Missouri series, and perhaps be an equiva 

 the Potsdam sandstone of New York. I cannot think that this sandstone and coi 

 erate should correspond to those in ( 4 ho-kup's Pass of the age of the ( )hl lied, alt 

 their appearance is similar; then the limestones would be of Carboniferous a< 

 they are quite unlike any I have observed in that series. 



An igneous protrusion, a spur of Mount Cooper, intercepts the further regul 

 cession of the strata. Near by some variegated and altered slates crop <>"t. A 

 points farther west in Kobah Valley small exposures of similar light-colored silio 

 nesian limestones were noticed. 



Near the north end of Kobah Valley I found some rock resembling seq 

 and other more compact basaltic ( ■ ) knobs. The mountains around the westei 

 of Kobah Valley are composed of igneous rocks, mostly porphyries, which si 

 hold a position between the dioritic and the trachytic group, and differ much ; 

 themselves; some of them present a peculiar appearance, and may be later intr 

 Others appear to be allied to the phonolites * Only near the southwest end of tl 

 ley, again some few stratified rocks of doubtful age were observed, sandstom 

 altered slates, and some greenish flinty siliceous strata, which have nearly h 

 marks of their sedimentary origin, by the immediate contact with the igneous 1 

 sions. 



The Pe-er-re-ah range is another of the principal chains. Near our trai 

 composed of granite, more recent eruptive, and some highly altered stratified 

 At the mouth of Simpson's Canon flint-rock and black and variegated slate; 

 noticed; a little farther on, white, coarse-grained granite, and soinemoiv finely--: 



* One specimen from Wons-in-damrne (Antelope) Creek, of wh i\ ;•■ uan, .-, renal 



closely specimens from the island of Ischia, near Naples, from the extii i ».•'■ asm I [. «.,, ,, th. i met ■•• - <»t w 

 now discharged by Vesuvius. Those specimens are a scoriaceous lava, altered by vapors of hydrochloric act 

 escape from the crater, and have converted the lava partly into kaolin. 



