ISLE OF MAN. ALLUVIA. 529 



magnitude and in accessible positions. Between Laxey 

 and Ramsey, in the neighbourhood of the Doon river, 

 they appear to have resulted from the ruin of the granite 

 which is there found in situ, since they possess an absolute 

 identity of composition with it, and differ from those 

 which are scattered over other parts of the island. As 

 they lie on the face of the hill above the present visible 

 part of the fixed rock, it is probable that this granite 

 extends to a much greater height in the mountains than 

 can now be ascertained ; and that some portions of it 

 might be found higher up, uninvested with the schistose 

 rock, if it were possible to remove the dense mass of 

 alluvial matter by which it is covered. 



Besides the granite, a few blocks of micaceous schist 

 may be seen in one or two places ; but of such a nature 

 that they may possibly be portions of the hills on 

 which they lie, since the intermixture of clay slate and 

 micaceous schist is by no means uncommon, as may 

 be deduced from several parts of the preceding descrip- 

 tions. 



Such are the most interesting phenomena which relate 

 to the alluvial matters found in the Isle of Man, and 

 such the very slender train of reasoning towards the 

 establishment of general results, which may be deduced 

 from them. But various other extraneous and transported 

 substances occur in different parts of the island ; and 

 as the account of them is too little interesting to require 

 a separate section, it will be preferable to make cursory 

 mention of them here. Whether such substances, gene- 

 rally found on the shores, have been brought among the 

 ballast of ships, or thrown up by the wash of the sea, from 

 distant rocks, is almost equally indifferent for the purposes 

 of geology. 



The scattered masses of different porphyries which are 

 seen in considerable abundance on the north end of 

 the island, must perhaps be referred to the general cause 

 which deposited the alluvia; since they are also found, 



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