170 



THE GEOLOGIST. 



oceanic conditions prevailed in the earliest epoch of the Glacial period. 

 Mr. Godwin- Austen has already enunciated a similar opinion.* 



The Irish submarine plateau is bounded by sloping sides, which 

 generally sink down to about 10,000 feet, or nearly 1700 fathoms, 

 before reaching the general level of the plain alluded to, with an in- 

 clination ranging from 400 to 1000 feet in the mile ; the lowest 

 being off Gal way (Hoskyn), and the highest on the coast of Kerry, 

 where, however, there is also a 548-feet incline. The surface of the 

 plateau appears to be marked by three terraces of different levels. 

 First. The outer edge of this, the lowest terrace, is not naturally 

 defined by the 200-fathoms line, as one of the names of the pla- 

 teau seemingly implies, but rather by one of 220 fathoms ; as it is 

 from the latter line that the most sudden descent is made into deep 

 water. Second. This terrace is limited by the 115-fathoms line, there 

 being here a well-marked break, before reaching shallow water. 

 Third. In passing from the last line to the shore, we meet with a 

 rise about the 35-fathoms line. It is not well defined ; but there 

 appears to be rather an abrupt ascent from 45 to 35 fathoms. When 

 these terraces were subaerial, the first was probably upwards of 1300 

 feet above the sea, the second nearly 700 feet, and the third upwards 

 of 200 feet. 



The vertical movements assumed as having taken place in subse- 

 quent epochs of the Glacial and Post- Glacial periods are in a great 

 measure based on the present premiss. 



4th. The first epoch of the Glacial period is generally admitted to 

 have been the coldest. It is my belief that the then British area, 

 with all the land now beneath the German Ocean, also that forming 

 the Irish "two-hundred-fathoms plateau," was shrouded with an 

 enormously thick pall of field- and mountain-glaciers. My views on 

 this subject are in no respect less ultra than those advocated by 

 Agassiz and Ramsay. Probably during the earliest portion of the 

 next or subaqueous epoch, the climatic conditions were not much 

 less rigorous : the removal of blocks from low to high levels, in the 

 way suggested by Darwin, requires the coasts to have been thickly 

 girded with ice, like the shores of east Greenland and other Arctic 

 lands at the present day. The close of this epoch appears to have 

 been affected by a somewhat milder climate, which continued into 

 the third (or second subaerial) epoch. If I am right in ascribing, 

 with Agassiz and Lyell, the origin of the Glen Roy terraces to a gla- 

 cier lake, it may be inferred that the last stage of this epoch enjoyed 

 a still more ameliorated climate ; probably ending with a mean tem- 

 perature more or less resembling that now prevailing in the British 

 Isles. 



5th. While I quite agree with Ramsay as regards the powerful de- 

 gradation which the rock-surfaces of the British area underwent 

 during the Glacial period, I must also contend, from what has already 

 been stated under the first of my premises, that our elevated regions 



* Quarterly Journal of the Geological Society, vol. vi. p. 86. I formed the opinion 

 before learning that Mr. Godwin- Austen had advanced a similar one. 



