524 MUCK. GEOLOGY. 



places a stratum of true amygdaloid of a loose texture 

 is seen under the simpler trap, but I observed nothing 

 sufficiently different from that which has already occurred 

 on the subject of the trap rocks, to render more particular 

 details on this part of the geology of Muck necessary. 



The only exception to the universality of trap in this 

 island is to be found at the bay of Camusmore, the only 

 spot which is interesting in a geological view. A series of 

 stratified rocks here comes to the surface, of which how- 

 ever but a very small portion is accessible, as the strata do 

 not reach to many feet in thickness above the low-water 

 mark.^ They have but a trifling inclination, dipping 

 towards the north in an angle not appearing to exceed 

 five degrees. They consist of different beds of sandstone 

 and limestone, of which the former are the lowermost 

 and the greatest in quantity. These are generally of 

 a calcareous quality, and are white, very much resembling 

 the sandstone which occurs in a similar situation in Egg. 

 The limestone verges from blackish blue to pale grey 

 and dove colour, becoming nearly white on the surface by 

 the action of the sea. Some of the beds contain the 

 remains of shells not easily ascertained ; in others the 

 rock is of a moderately fine granular texture ; while in a 

 third set it has a flat conchoid al fracture, with the smooth 

 surface and brit.leness of glass. 



These beds are traversed by sundry veins of trap of dif- 

 ferent aspects and compositions, undergoing at the same 

 time great disturbance. The trap is sometimes porphy- 

 ritic, at others it has the aspect of an ordinary dark blue 

 basalt, and in one or two instances the vein which is 

 dark blue and hard in the middle, becomes of a very pale 

 smoke blue at the edges, acquiring in those parts con- 

 siderable softness. The limestone, which is of a coarse 

 grain at a distance from the trap, often assumes a fine one 

 with great brittleness in its vicinity ; while in other cases 



* Plate XXXII. fig. 2. 



