534 ISLE OF MAN. GEOLOGY. 



mineral composition will explain the causes of these varia- 

 tions. I may here remark, that, in many instances, these 

 varieties present an ornamental disposition of colour, some 

 of the rocks also, consisting of breccias of considerable 

 beauty; but their irregularity, their hardness, and the 

 numerous fissures by which they are intersected, prevent 

 any temptation to work them as marbles. 



The chief variations in the stratified limestone are those 

 in the colour, in the quantity of organic remains which 

 it contains, in the greater or less admixture of argil- 

 laceous and siliceous earths, and in the quantity of shale 

 which occurs interlaminated with the beds. In conse- 

 quence of these variations, the different beds are more 

 or less adapted to the several purposes, whether of mortar, 

 or of agriculture, and different quarries are accordingly 

 opened in various places, to which, according to the 

 purity of the produce, more or less value is attached. 

 Those of Balla salla are by far the most extensive ; but 

 it is unnecessary to enumerate all the quarries which have 

 actually been wrought. 



At Pool vash, and within extreme high-water mark, 

 is found a series of beds, of a very dark colour approach- 

 ing to black, which have long been wrought as marble- 

 They possess a sort of historical celebrity from having 

 furnished the steps which ascend to the entrance of St. 

 Paul's Cathedral ; a present, as is well known, from the 

 bishop of this diocese. They are now wrought for grave- 

 stones only, since they are, from their argillaceous nature, 

 incapable of receiving a polish. 



The next and last rock is a small tract of red sandstone, 

 which, on account of its insignificant geographic extent, 

 is here described last, although, in a geological view, 

 it must rank before the limestone. It commences about 

 half a mile to the north of Peel, at the end of a small 

 sandy bay, and is continued along the shore for the 

 space of about two miles, where it terminates, being imme- 

 diately succeeded by the schist already described. Its 



