281 



to those small fissures alone. I shall describe one of another kind, in 

 the observations at station No. 14. 



When the basalt was erupted and cooled, and those fissures all left 

 full of solid trap, as whin dykes, the mountain parts were elevated, and 

 at the margin of the trap district continued steep and high, from those 

 numerous dykes, which, having hardened, became as so many wedges 

 along the line, increased the volume of the rock, and served to keep this 

 line more elevated than the other localities where those dykes are not. 

 They also served, very probably, as strengthening ribs, when cold, 

 along the outcrop of the chalk, to offer greater resistance to the denud- 

 ing power, or keep the outcrop to a higher level. 



12. Ballygilbert is nearly three miles north of Sallagh Braes. The 

 limestone at this place is 530 feet high ; and it covers the slope from 

 where it appears down to the shore, something more than half a mile. 

 Wherever the limestone spreads out, and occupies the country in this 

 way, its thickness cannot be measured. 



\3. Glenarm is three and a half miles from Ballygilbert, 'No. 12. 

 Where the limestone was measured here is at the northern boundary of 

 Little Deerpark, on the shore, 1 84 yards west of the little quay. This 

 is about half a mile east of the town. Here the limestone is 1 70 feet 

 thick, and its base appears to be at high water mark at this spot. 

 From this westward it dips into the water, so that at the large quarry, 

 near the town, about half the mass of the chalk is under sea level. 

 From Ballygilbert to Glenarm the limestone band begins again to as- 

 sume the character of an outcrop, and maintains this character by Gar- 

 ron Point and Cushendall, in all its windings to the north and west 

 from Glenarm. 



Through the Little Deerpark, the steep face of the mountain, for a 

 mile or more in length, exhibits a multitude of masses of chalk rock, 

 that slipped down from the outcrop even to the very shore. This steep 

 slope may be about half a mile wide. Lias clay shows itself in many 

 places, and it is owing to this that the slips take place ; for this clay, 

 though a bed of solid rock, becomes quite soft when water gets access 

 to it through fissures in the overlying rock. When this soft founda- 

 tion gives way under the chalk, it is the cause of more fissures, more 

 water, and more slips afterwards. 



At the quarry at Glenarm, and on the shore, the chalk is visible. 

 At the mouth of the river it sinks under the level of the water 

 altogether, and for miles up the river there is none in the face of the 

 east side of the valley, where it might naturally be expected, as this is 

 the case in most of the glens. At Parishagh, on the west side in the 

 slope of the hill, half a mile off, the chalk stands at about 350 feet high, 

 and continues on the north-west side of the valley for some miles up. 

 This difference of level shows that there is a fault in the line of the 

 river, or rather in the bottom of the valley running to the south-west, 

 and that to the east of this fault the land has sunk, and buried the 

 limestone in the fault. The limestone at Ballygilbert on the south, 

 where it stands at 520 feet high, has a fall from this place to Glenarm 



