ISLA. GENERAL DESCRIPTION. 



may vaiy in the time of their arrival, there is thus pro- 

 duced in some cases a counteraction, in others a coinci- 

 dence. In a similar manner, the situations of headlands 

 divert the course of the stream : in some cases they receive 

 the impulse of two streams, and there are thus produced 

 still further intricacies, accompanied by those eddies and 

 gyrations, and that breaking sea, which render so many 

 parts of this coast dangerous to boats. An accurate know- 

 ledge of these tides is not unimportant to the geologist who 

 may attempt the voyage of the Western islands ; since, with- 

 out it, he will often be defeated in his objects and find it 

 impossible to reach the points which he is desirous to 

 examine. At all times he is their slave, and can only 

 defeat them by a watchful attention to their movements. 



From the point of the Rinns, along the west side of 

 Loch in daal, there is a succession of low rocks and 

 alluvial land, terminating beyond Connisby in a large 

 shallow sandy bay, which, with the exception of the rocky 

 point of Laggan, is continued to the promontory of the 

 Oe. Here, a range of high cliffs occurs, reaching round 

 the Mull of Oe to Loudinas ; the point of the promontory 

 rising to a precipitous height of 800 feet or more, and 

 presenting that scenery of which I have just made cursory 

 mention. The eastern coast, as far as Ardtala, consists of 

 a rugged line of low rocks, much indented, and beset with 

 islands ; the quartz rock here forming the higher and 

 more precipitous shore of which Macarthur's head is the 

 most conspicuous point, and which terminates in the 

 sound whence this circuit commenced. 



In describing the general surface of Isla, it will be con- 

 venient to divide it into regions, as this will not only render 

 the geographic descriptions more intelligible, but conduce 

 to a clearer understanding of the geological details. The 

 first of these is determined by five points ; Ru val, Loch 

 Gruinart, Octofad, Isla house, and Portaskeg; and the 

 peninsular division to the south of this may be considered 

 as the second: the terms of north-western and south- 



