ISLE OF MAN. ALLUVIA. 



of the island where the operation of such a cause 

 seems far less doubtful, nay, even probable. 



This is the northern flat district already noticed in the 

 general description, including the Curragh and the Balla 

 chyrrim hills, and terminating on all sides in a shore of 

 pebbles, or in an abrupt face of clay, sand, marie, and 

 similar loose materials. There can be no question that 

 such deposits have been formed from the ruin of solid rocks 

 at some distant period ; and nothing that is visible in 

 the present structure of the land, nor any thing that 

 can be imagined of its former shape, will justify us in 

 supposing that the deposit in question has been produced 

 by rivers formerly flowing from the summits of the 

 present hills, or of any hills occupying their position. 

 The presence of granite and porphyry in this alluvium, 

 substances scarcely existing in the island, prove that 

 they have been brought from distant points. If even 

 any imaginary former altitude of the present moun- 

 tains be assumed, the well known laws which predo- 

 minate with respect to the relative positions of rocks, 

 do not permit us to assign a place for the granite 

 whence the granitic fragments should be derived, had 

 they resulted from the decomposition of former moun- 

 tains existing in the island. It will hereafter be seen, 

 that the low position and small extent of the granite 

 in this island, prevent it from offering an exception to 

 the conclusion here drawn. 



It is more probable that the alluvium in question has 

 been the result of a general diluvian action, directed from 

 the south towards the north, nearly in the present line 

 of the channel which separates England from Ireland. 

 Thus the deposit has been formed under the shelter of the 

 hills ; having been subsequently modified, in all probability, 

 by various causes of more tedious operation ; namely, by 

 the effects of the tides, by the action of the currents as their 

 position becomes gradually altered in consequence of their 

 own attacks on the yielding materials of the bottom, and 



