PACIFIC AND BEERING'S STRAIT. 181 



of compact basalt, containing the imbedded minerals c vi P ' 

 which characterise that formation, and bearing a ^^^ 

 close resemblance in this particular to the basaltic lrae?. 

 formation of the county of Antrim in Ireland. 

 There is, however, less of the basalt and more of 

 the porous. The zealites, soapstone, chalcedony, 

 olivine, and calcareous spar, are formed in, and 

 connect the relationship of these distant formations ; 

 whilst the different-coloured jaspers are peculiar to 

 these islands. There is also another obvious dis- 

 tinctive feature produced by the numerous dykes of 

 a formation differing in composition and texture, 

 and marked by a defined line. They are generally 

 more prominent than the common rock ; traversing 

 a great many, if not all the islands, in a direction 

 nearly east and west ; generally about eighteen 

 inches wide, nearly perpendicular to the horizon, or 

 dipping to the southward. Their texture is some- 

 times compact, sometimes vesicular, with few if any 

 imbedded minerals, excepting one on Marsh Island, 

 which contained great quantities of olivine. Upon 

 a small island contiguous to this, the harder dyke 

 crosses the highest ridge, and divides on the eastern 

 side into two parts which continue down to the 

 water's edge."* 



Lieutenant Belcher, whose scientific attainments 

 also enabled him to appreciate what fell under his 

 observation, noticed every where the trap formation 

 abounding in basaltic dykes also lying N. E. and 

 S. W., and seldom deviating from the perpendicu- 

 lar ; or if they did, it was to the eastward. We are 

 indebted to him for specimens of zealite, carbonate 



* Mr. Collie's Journal. 



