THE GEOLOGY, PHYSICAL FEATURES, 

 BOTANY, AND VERTEBRATES OF 



THE OUTER HEBRIDES. 

 BY THE REV. WILLIAM MORRISON, M.A., CARR BRIDGE. 



" THE LONG ISLAND," as this chain of islands forming the 

 Outer Hebrides is named, extends from Barra Head to the 

 Butt of Lewis. Geologically it is interesting, as it forms a 

 huge breakwater to the Atlantic, which otherwise would 

 have long ago swept away the later formations which com- 

 pose the Inner Hebrides, and would have made serious 

 I inroads on the western seaboard of the mainland. The 

 ! rock formation of the Outer Hebrides stands out as a 

 | solid wall of Archaean age, breasting the billows of the 

 ! ocean in their ceaseless assault upon our islands. True, 

 the upper tiers of that wall have gone by marine erosion 

 I when the " Long Island " was submerged under the waters 

 i of the Atlantic, but as these tiers of later rocks were removed, 

 | the basement rose as a bulwark against the breaching action 

 of the sea. This accounts for the general flatness of those 

 islands. On the mainland of Sutherlandshire the same 

 rock formation is seen levelled down with almost mathe- 

 matical precision, and on this level platform the huge 

 masses of the Torridon Sandstone formation rises to 

 thousands of feet into the air. These Torridon Sandstones 

 in vast sheets run from near Cape Wrath to the 

 Lochcarron, and give an impressive idea of the appalling 

 i antiquity of the underlying rock formation of the Archaean 

 rocks of the Outer Hebrides. Standing on these Archaean 

 rocks, we really stand on the basement of the geological 

 [staircase of the globe. This basement rises nowhere to 

 ;hills of over 3,000 feet. The "outliers" or peaks of the 

 formation may be seen in North Rona, the north part of 

 jRaasay, Coll, Tiree and lona, but in their greatest extent 

 ;in the islands of the Outer Hebrides. St. Kilda is geologi- 



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