Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/136

 extremity of the chain is the highest summit, it rises 1820 feet above the level of the sea; but the basis of this mountain is occupied to the height of 500 feet by primitive rocks, (connected with that district of mica slate which has been before mentioned as appearing in this part of the country) leaving only 1320 feet for the thickness of the secondary strata peculiar to this system. Diris hill, near the southern extremity of the chain, is wholly composed of those strata and attains an elevation of 1475 feet above the sea: it is situated about two miles to the west of Belfast.

On the S.E. this chain pours several small streams into Belfast Lough, and on the N.E. into the North Channel; all these have a very short course. On the west three rivers of rather more importance take their rise; the six mile water and the river Main which flow into the bay of Antrim in the N.E. angle of Lough Neagh; and the Bush which empties itself into the ocean a little west of the Giants Causeway.

The western chain included between the Roe and the Bann forms the exact counterpart of the former, but the strata here dip in a nearly contrary direction, namely, towards the north-east; the fall of the hills being gradual in this direction, while they front the west and south with abrupt and precipitous escarpments. Cragnashoack at the southern extremity, is as might be expected from this general of the line, the highest summit, it rises 1864 feet above the sea, exceeding by 44 feet the loftiest point of the eastern chain. Slieve Gallion, an insulated hill which stands in an advanced position at some distance from the south bank of Cragnashoack is less elevated by 240 feet.

Benyavenagh, the extreme mountain on the north, is one of the lowest in the chain, rising only 1114 feet.

The Roe, the Clady, and Aghivey, are the principal water courses