62 Guide to Belfast. 



treated. The entrance to the lough is about one-third of a 

 mile wide and about five miles long. Here, at certain states 

 of the tide, the current runs at from 5^ to 7 knots for 

 ordinary tides to 9 knots an hour for some spring tides, 

 generating whirlpools that are dangerous to boats attempting 

 to enter the lough. We are led to suppose that its present 

 outlet dates from the end of the Glacial period. Before this, 

 its basin, from evidence found in the glacial deposits to the 

 south of the district, seems to have been shallower than at 

 present, containing a large deposit of Carboniferous limestone. 

 The pre glacial entrance was probably situated between Ard- 

 glass and Dundrum. Between these points we find extensive 

 deposits of glacial sands and gravels, with a large percentage 

 of Carboniferous limestone erratics; and the district known 

 as Lower Lecale, from Downpatrick to the east, bears 

 evidence of extensive glaciation, the striae running N.N.W. 

 and S.S.E. 



The next coast indentation is Dundrum Bay, bounded on 

 the north-west by extensive sand dunes. Carlingford Lough, 

 nine miles long and about two miles wide, separates County 

 Down from County Louth, and is bounded on either side 

 by the steep slopes of the Mourne mountains and Carlingford 

 mountains. 



Drainage and Rivers. 



The county of Antrim possesses one main watershed, 

 embracing the summits of the hills that occur parallel to the 

 east coast. It follows the line of hills parallel to Belfast 

 Lough in a N.E. and S.W. direction. The following are the 

 chief peaks or eminences in the crest beginning from the 

 north: Carnanmore (1,254 feet), overlooking Torr Head; 

 Slieveanorra (1,676 feet), at the head of the Glendun river; 

 Trostan (1,817 feet), Collin Top, Slemish (Slieve Mis, 

 1,437 feet), Agnew's Hill, Cave Hill (Ben Madighan, 1,188 

 feet), overlooking Belfast ; Black Mountain and White 

 Mountain, a few miles north of Lisburn. This line of 

 summits deviates from the straight line, where the water- 

 shed has been eaten back by the rivers that have excavated 

 the valleys forming the Glens of i\ntrim. To the east of 

 it the rivers flow into the North Channel with steep and 



