122 G. M. DAWSON — COASTS OF BERING SEA AND VICINITY. 



usually low and flat, the highest point, at the western end, being, accord- 

 ing to the chart, about 800 feet. The islands slope down to the south- 

 ward with nearly uniform grassy surfaces. 



Attic Island, — This is the westernmost island of the Aleutian chain. It 

 appears to be throughout mountainous, and, in its general contour, with 

 steep, grassy elevations, closely set, is not unlike most of the larger islands 

 of the chain. Its highest point, according to the chart, is 3,084 feet. 



My observations were confined to the vicinity of Chichagof harbor, on 

 the north side of the island. At the east end of the gravelly beach at 

 the bottom of the harbor, hard, greenish gray rocks occur, possibly dia- 

 base in composition, but too fine grained for macroscopic determination. 

 These are in some places distinctly bedded and probably clastic, the dip 

 being north 65° west (magnetic), at an angle of 45°. Similar rocks, with 

 a similar dip, appear on the opposite side of the harbor at the west end 

 of the same gravel-beach, and were again found at the summit of the 

 mountain or high ridge on the east side. The rocks of Gibson island, off 

 the mouth of the harbor, were observed to be bedded with such unusual 

 regularity that this island was specially visited. They proved to consist 

 for the most part of much altered and indurated volcanic materials, with 

 purplish, greenish and gray colors. Perhaps the most abundant material 

 is a medium grained rock, w^hich in some specimens is evidently an erup- 

 tive, in others probably clastic, and very possibly a diabase in composi- 

 tion, but fine grained clastic felspathic rocks also occur, which pass into 

 a black compact material which is apparently a true argillite. Though 

 sought for, no fossil remains of any kind could be found. The dip is 

 here north 30° east (magnetic), at an angle of 40°. 



The rocks seen in the harbor closely resemble those noted in Nazan 

 bay, Atka island. The general lithological character and degree of altera- 

 tion of the rocks of this part of Attn island resembles that of some of the 

 Mesozoic rocks of British Columbia, particularly parts of the Triassic 

 series as represented there, and though such a criterion is of very limited 

 value, Dall may not improbably be correct in his conjecture that they 

 are of Mesozoic age.* In any case, the high angles at which these rocks 

 lie and the amount of alteration and denudation which they have suf- 

 fered show that beds much older than those referable to modern or even 

 late Tertiary volcanic action are included in the composition of this part 

 of the Aleutian chain. 



Dr Dall states that Attn is destitute of modern volcanic rocks, and my 

 observations, so far as they go, are to the same efi'ect. Even in the gravel 



* Op. cit., p. 344. The occurrence of Triassic rocks in the peninsula of Alaslia is indicated by 

 specimens from that peninsula shown to me by Mr R. Neumann, of Unalaska. These consist of 

 the Monotis-beaving argillite of that formation. 



