212 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [Jan. 22, 



Clew Bay, to glaciation at 2000 feet upon a hill-top near Galway 

 Bay. But this quartz hill stands there like the stone pillar at Penryn, 

 to mark, 1st, the depth of the ice, and, 2nd, the depth of the rock 

 which has been removed from that region. On lower hills are marks 

 of local Connemara glaciation ; but at the head of Galway Bay is a 

 bed of Boulder-clay full of limestone from the central regions, rest- 

 ing upon rocks striated in the direction of the sea. A great body of 

 ice at some time or other passed off Ireland from the N.E. to S.W. 

 by way of Galway, according to the high and low marks which I 

 more fully described in ' Frost and Fire,' and which are now mapped 

 by the Geological Survey *. 



The high marks upon Shan Folagh pointed the way to seek for 

 more knowledge nine years ago. The lines ruled upon the hill-top 

 were produced upon a map, and touched Cushendal, in Antrim. In 

 1872, after nine years, I went there to see what I could find. I 

 found first unmistakable marks of a local Antrim system propor- 

 tionate to the size of the hills. 



Next I found out a tall trap-hill called Slieve Mish, and went to 

 the top of it. I found it a great glaciated " Tor," beside a rock- 

 groove which crosses the range. In the groove, at about 500 feet 

 above the sea-level, I found and copied stria? pointing N.E. and 

 S.W. ; therefore this groove was filled with ice of some kind. The 

 long axis of the hill is nearly north and south ; the rock is wea- 

 thered ; but at the northern end it is deeply grooved. If these are 

 old weathered ice-marks, as I believe them to be, then all the marks 

 aim right over Ireland at the Twelve Pins of Connemara, and over 

 the sea at the Firth of Clyde. In mapping the glaciation of Ireland 

 a line may fairly be drawn from Shan Folagh to Slieve Mish, and the 

 ancient ice may be reckoned to have been more than 2000 feet deep 

 from one side of Ireland to the other, within the bounds of Ulster 

 and Connaught. That makes the northern ice-system in Ireland. 



Theoretical General Glaciation. 



Of late years a school of geologists have taken up a glacial theory 

 which their adversaries condemn. The advanced glacial theory, so 

 far as I understand it, is that during a late geological period the 

 whole of the Northern Hemisphere, from the Pole down to regions near 

 the Equator, was covered by a continuous thick crust of ice. It grew 

 then, as ice grows now, by evaporation about equatorial regions and 

 by condensation about the Poles and about high grounds. From the 

 Polar regions, where the ice was many thousands of feet deep, as 

 from the chief condensing-point and gathering-ground, this general 

 ice-system spread southwards, because any pile of plastic materials 

 so spreads. No one imagines that all the water evaporated con- 

 densed at any one spot, at the Pole or elsewhere ; but the greatest 

 condensation was about the coldest region near the Pole. 



Accordingly the ice moved thence with a general southerly move- 

 ment, along meridians, during the greatest development of the last 



* A specimen from the hill-top was shown. 



