Palieo-Geolojical and Geographical Maps of the British Islands. 287 
Puates XXXIV. anp XXXYV. 
The Glacial, or Post Piiocene Period. 
The Glacial or Post Pliocene period has been generally, and, as I believe, cor- 
rectly, distributed into three distinct epochs, which merge into each other but were 
each of prolonged duration. During each epoch the climatic conditions, the rela- 
tions of land and sea, and the resulting deposits, were different, and may be briefly 
tabulated as follows for the area of the British I[sles. 
THE GLACIAL PERIOD. 
Epoch or Stage. Terrestrial Conditioas. Climatic Conditions. Formations. 
3. Upper, 7 Partial submergence, : Sub-arctic, 5 Upper Boulder Clay. 
2. Middle, 6 Deepest submergence, : Teiperate, ; Middle Sand and Gravel. 
1. Lower, : Greatest elevation of land, Arctic, : Lower Boulder Clay or Till. 
Between these deposits and the Norwich crag are some interesting Glacial or 
sub-Glacial beds, indicating the approach of the Arctic conditions which prevailed 
during the formation of the Lower Boulder Clay.” 
Plate XXXIV. represents the physical conditions of the British area during the 
Lower Glacial stage, represented by the Lower Boulder Clay (epoch or stage 1), 
and the general glaciations of the exposed rock surfaces. It will be observed, that 
the whole of the present area of the German Ocean, as far south as lat. 51° 30’, 
was filled with a great ice-sheet, stretching southwards from the Scandinavian 
peninsula,+ which, at that epoch was covered, like Greenland at the present day, 
with a continuous sheet of snow and ice. ‘This ice-sheet became divided into two 
divergent sheets in lat. 57 30’ owing to the obstruction to its course caused by 
the position of the Scottish Highlands and the large masses of ice descending in 
an easterly direction from the snowfields of the Grampians. While one portion 
took a south-westerly course towards the Norfolk Coast, another moved in a 
direction perpendicular to this, and passing over the Orkneys,t and the northern 
end of Caithness in an N. W. direction,$ protruded outwards into the Atlantic. || 
The Scandinavian ice-sheet, however, does not appear to have extended to the 
Faroe islands, which, as Dr. J. Geikie has recently shown, were glaciated by ice, 
having a strictly local origin amongst the central heights of these islands them- 
* These deposits are included in Mr. J. S. Wood’s “ Lower” and “ Middle” Glacial series ; but as Dr. 
J. Geikie has shown, they are of older date than the three stages given above.—“ Great Ice AMEGB” iy 
370 (1874.) 
t Croll, “Climate and Time” p. 444. 
+ Peach and Horne, Quart. Journ. Geol. Soc. vol. XXXVL, p. 648. 
§ T. F. Jamieson, Jbid., vol. xxii. p. 261. 
|| Dr. Croll, Zb¢d., Map. p. 449. Mr. Croll takes the margin of the ice-sheet much further westward in 
the Atlantic than that shown in Plate XXXIV. It would be impossible to determine the true limits, 
which in all cases must be hypothetical. 
