1879-1880.] 405 



Leaving the hill-top by a path lately constructed, and admirably 

 designed to afford good views of the rich scenery from its con- 

 venient resting-places, a visit; under the guidance of Mr. Harbi- 

 son, was made to the quarries on the southern flank of the hill. 

 Here the junction between the basalt, which forms the higher 

 ground of the hill, and the sandstone in which the quarries are 

 worked, is well seen, and several horizontal intrusions of basalt of 

 older date than that which forms the summit are also well exposed. 

 The large dyke, or filled up fissure, which probably gave vent to 

 the molten material of the later outflows, was also pointed out, as 

 well as its action in altering the sandstone through which it has 

 cut. There is, therefore, in this quarry quite a number of 

 phenomena of igneous rocks to be observed, which, if thoroughly 

 mastered by the geological student, would simplify much that 

 might appear most puzzling. Proceeding towards the opposite end 

 of the hill, all were much surprised at the extent of the quarries in 

 progress. Here again the student will find much to interest him. 

 It is to the geologist an elementary truth that our sandstone rocks 

 are simply the sand deposited on the shores of an ancient world, 

 rendered cohesive by some cementing substance, and hardened by 

 superincumbent pressure. This fundamental truth has been 

 sufficiently established by geological writers; but at Scrabo 

 quarries it is displayed in such a palpable manner that " he who 

 runs may read." A large extent of the quarry floor consists 

 of the rippled surface of an ancient beach, as perfect as when 

 the tide receded from the shore. Thus, the waters in which 

 the new red sandstone was deposited — that is, if an inland sea, 

 as some persons suppose — were at all events sufficiently exten- 

 sive to have tides like our present oceans. These instructive 

 ripple-marked surfaces were well examined ; and also, in close 

 proximity, another phenomenon of similar import — viz., the sun 

 cracks displayed on the same rocks. These are identical in 

 character with the cracks now formed by the heat of the sun in any 



