422 PABBA. GEOLOGY. 



PABBA.* GUILLEMON. 



THE flat and fertile island of Pabba is of a roundish 

 figure and about three miles in circumference ; lying 

 between Scalpa and the coast of Sky in a direction corre- 

 sponding in such a manner with that of the limestone 

 beds of Broadford, as to indicate its composition even 

 before it is examined. 



It forms a flat table scarcely sixty feet high, the south- 

 eastern side being elevated and abrupt, while the opposed 

 one declines to the water's edge ; the whole being sur- 

 rounded by low reefs of rocks causing a foul shore. Its 

 structure tallies so exactly with that of the analogous 

 points about Broadford, as almost to render a particular 

 description superfluous. It is however necessary to notice 

 it, on account of the aid it offers in connecting the several 

 scattered portions of rock which are found in the neigh- 

 bouring islands and on the adjacent mainland. 



The rocks towards the south-east consist entirely of the 

 micaceous shale already described in speaking of the Broad- 

 ford strata. This substance is tender and readity acted on by 

 the sea ; and although appearing very solid when examined 

 in a mas$, is easily split into thin and mouldering laminae. 

 The dip is only five degrees and is to the N. W., in which 

 respects it also corresponds to the beds at Broadford. 

 Numerous rounded nodules of trap are contained in these 

 beds of shale, being very remarkable in consequence of 

 their superior permanence. They are all decomposed at 

 a certain depth from their surfaces, a change apparently 

 prior to their present position, since it equally exists in 

 those which are deeply imbedded in the surrounding sub- 

 stance. On the western side of the island portions of the 

 other Broadford strata are found but as they differ in no 



* Pab, stubble Gaelic. See the Map of Sky. 



