289 



\"iewed from the sea, the lowland presents the appearance 

 of three gigantic steps. The highest step at an elevation 

 of about 140 feet (42 m.) is not well preserved; but the 

 lowest two, at elevations of 20 (6 m.) and 40 feet (12 m.), 

 are sharply defined. Each represents a wave cut beach. 



For splendid exposures of Silurian rocks of great thickness 

 there are few regions which surpass that of Arisaig. The 

 shore cliffs are well developed and these with the sections 

 exposed in the brook gorges show the Arisaig region to 

 consist of large blocks, bounded by faults of great magni- 

 tude, so that a structural and formational map of the 

 region forms an irregular mosaic. The fault of greatest 

 displacement is that separating Eigg mountain from 

 the narrower block of Silurian hills which fronts it. On 

 the land the locus of the fault zone is plainly shown by 

 the pronounced structural depression known as the Hollow 

 which can be followed westward to Bailey's brook while 

 its northeastward extension forms the straight coast 

 reaching nearly to the end of the peninsula of Cape George. 

 The downthrow of the Silurian block proved its preser- 

 vation, but in its descent the drag along the fault zone 

 produced an asymmetric synclinal trough, the rocks of 

 which are criss-crossed by myriads of small faults and 

 fractures. 



PREVIOUS WORK. 



The first student of the Arisaig sequence was J. W. 

 Dawson, who investigated the region previous to 1845. 

 He was succeeded by David Honey man, who began his 

 studies there about 1859. Following Honeyman came 

 Fletcher, Faribault, Ami, Schuchert, Twenhofel, and 

 Williams; each of whom has studied the section in whole 

 or in part and in their published results have built up 

 our present knowledge of the region. A compilation of 

 their results is summarized in the following table of for- 

 mations. 



35063— 6a 



