310 SCIENTIFIC NEWS. 



The circumference of this island is about two miles : it 

 forms a kind of tableland of i. regular surface, gently sloping 

 to the N. E. and is bounded on all sides by steep and generally 

 perpendicular cliffs from 60 to 70 feet above high water mark, 

 the greatest elevation in the island being about 120 feet. 



The entire island is a mass of basalt, but a bed of sandstone 

 is sard to be visible at low water on the western side. 



The basalt presents two varieties, the columnar and amor- 

 phous, the latter of which is generally amygdoloidal, con- 

 taining zeolites. In the columnar variety lamellar stilbite-is 

 % occasionally found filling the intervals of approximate columns, 



and sometimes, though rarely, in the substance of the smaller 

 and more irregular columns. 



On the south-western side of the island there appears to be 

 three distinct beds of basalt, the lowermost of which seems 

 to be amorphous. The next bed from 30 to 50 feet thick, 

 consists of those large columns which form the most conspicu- 

 ous feature of Staffa. The upper one appears at a distance to 

 be a mass of amorphous basalt, but on closer inspection is found 

 to consist of small columns, often curved, laid and entangled 

 in every direction. The columnar basalt of Staffa is by no means 

 so regular as that of the Giant's Causeway } but in return it pre- 

 sents many beautiful specimens of bending columns, which do 

 not occur at the latter place ; of these the most remarkable 

 form a conical detached rock called Budchaille, or the Herds- 

 man. Besides the great cave are two smaller ones, which 

 being accessible only by a boat, and in perfectly calm weather 

 can very rarely be examined. 



The surface of the island is in some places overspread with 

 a bed of alluvial matter, containing rounded fragments of 

 granite gueiss, mica slate, quartz, and red sandstone, together 

 with a few rolled pieces of basalt. As there is at present a 

 considerable extent of deep sea between this bed and the 

 nearest primitive rocks of Jona, Coll, Tirce and Mull, it be- 

 comes an interesting subject of speculation to inquire into the 

 conditions Yequisite to account for this fact, there seems to be, 

 either that a declivity sufficient to allow of the transportation of 

 rounded fragments has formerly existed, sloping upwards from 

 the present level of Staffa to some primitive mountains, which 

 &o longer exist, or that the whole island of Staffa itself has 



been 



