J. STANLEY-BROWN — THE PRIBILOF ISLANDS. 490 



An uplift then gave to must of the island an additional elevation of 200 or 300 

 feet, accentuated the ridges formed by the outpours, gave them a monoclinal aspect 

 by converting their northwesterly fact's into bluffs as steep as they could he made 

 by great blocks of broken lava, and formed shallow troughs between them and the 

 shores. The parallelism of the faults is well displayed to any one standing on the 

 summit of the central vent. 



With two exceptions the lavas of the islands are basalts identical with those of 

 Saint Paul, save in the alteration of their olivine. The decomposition of the olivine 

 is in all stages of advancement, accompanied by the formation of red oxide of iron. 

 Otherwise it would be impossible to distinguish these lavas, microscopically, from 

 the rocks of Saint Paul. 



On the northern shore of the island, at a point just east of the village, a basaltic 

 dike from 2 to 3 feet in thickness and parallel to the ridges, cuts through the tuff, 

 which here overlies and rests immediately upon the floor lava. This dike, though 

 a true basalt, differs from the adjacent rock in that it contains enstatite in addition 

 to the usual augite. Just opposite this dike, at ( rarden cove on the southern shore, 

 Mr. Elliott* states that he noted a " large dike of bluish or greenish-gray phonolite, 

 in which numerous small crystals of spinel are found." Unfortunately this dike 

 could not be discovered by me on my visits to Garden cove, but there is at that 

 locality a large mass of compact greenish-gray peridotite, which dips northeastward 

 at about 45°,and upon the upturned edges of which rest, unconformably, the over- 

 lying lavas. The area of this mass and its relation to the other material cannot he 

 entirely made out. The peridotite is composed of enstatite and olivine, and ser- 

 pentinization is well advanced. 



At the only two points on the island where the shores are lowlying, the floor of 

 dark vesicular lava is horizontal and near the level of the water. This may not in 

 all cases be due to wave action. ( hit lying reefs are rare, and the water surrounding 

 the island is, as mariners say, " bold." The earlier constructional forms are nearly 

 obliterated; no true crater remains intact; and hence the cuprshaped depressions 

 at the summits of the cones and vents of Saint Paul are here lacking. No natural 

 cairns or volcanic tunnels are to be seen, and the surface lavas along the ridges often 

 have the form of plates, of all degrees of thinness, that ring like porcelain when 

 1 rod upon. There are no marks of glaciation or of erosion, and no erratics occur. 

 Disintegration is apparently the only process now going on. 



There remain two other tiny members of the group, Otter and Walrus islands, 

 each about (i miles oil' the shores of Saint Paul ; but their geologic story is SO similar 

 to, arid so identified with, that of their greater neighbor that, for the sake of brevity, 

 its recital is omitted. 



There are two fragments of paleontologic evidence connected with the islands 

 which, as they have been used by writers, demand a cautionary word. The tusk 

 of a mammoth was found in the sands of Northeast point on Saint Paul island, and 

 the tooth of one is reported as coming from the shores of Sainl George. As there 



is not a foot of earth upon either island, save that which has resulted from the 



decomposition of the native rock and the decay of vegetation, the value of puch 

 tesl imony is questionable. 



Small as the I'rihilofs are, they afford ground for differences of opinion. In 

 writing of these islands, Mr. John Muiri bas said that they "appear in general 



\i-i i- Proi i ." p. ■_"J7. 



| Arctic ('nil iiK' Revenm Cuttoi C'orwin, 1881 Notes uiul Olmerviil ions," p 1 1". 



