542 ISLE OF MAN. GEOLOGY. SCHIST. 



either massive or fissile, or appears under the two modifi- 

 cations of graywacke and graywacke slate. 



This rock, in its different forms, is found in every 

 part of the island, but the massive is every where more rare 

 than the fissile. Wherever it occurs, it is irregularly 

 interposed among the clay slate, often in portions ex- 

 tremely small, sometimes forming larger tracts, and there- 

 fore alternating with it in an irregular manner. This 

 alternation appears, in some cases, to take place by beds ; 

 in others, the portions of the graywacke mixed with the 

 clay slate, are so irregular and so dispersed, that it is im- 

 possible to determine whether or not they possess any 

 fixed relation to it. Examples of these occurrences are so 

 numerous, that it is superfluous to enumerate them : I 

 shall describe only two, because of their distinctness and 

 of the facility with which they may be examined by 

 those who may be so inclined. 



Where the junction of the red sandstone with the primary 

 rock at Peel takes place, a fine fissile clay slate is found in 

 immediate contact with the sandstone. A few thin beds 

 of a non-fissile graywacke, extremely reticulated by veins 

 of quartz, alternate with this slate ; and it may be remarked 

 that the quartz veins are limited to the former, never 

 passing into the latter. The graywacke breaks into 

 irregular angular fragments, having no apparent rela- 

 tion to the general fracture of the schist. In the same 

 place, a repeated alternation is also visible, of an ex- 

 tremely fine and soft clay slate, of a blue and of a black 

 colour, with a similar graywacke. The clay slate is in 

 thin beds, which are prolonged, and, as it were, com- 

 pressed between the graywacke ; being at the same 

 time bent or twisted, so as to put on the deceptive 

 appearance of veins.* The unequal action of the sea 

 and weather on these two substances, renders this 



* Plate XXVIII. fig. 2. 



