216 NEOZOIC TIME. [CHAP. XI. 



which the soundings are seldom more than 500 fathoms, 

 and are more often between 300 and 400 ; this, then, may 

 indicate the site of the connecting land which existed 

 throughout Eocene, Oligocene, and Miocene times. To 

 effect such a union now would require an elevation of 

 about 3,000 feet, and it seems reasonable therefore to re- 

 gard this as a rough measure of the difference in altitude 

 between the base-levels of modern and Eocene Scotland. 

 If to this we add the present heights of Scottish moun- 

 tains, and allow 1,000 feet as the amount by which they 

 have been lowered since the commencement of Tertiary 

 time, we have a total of over 8,000 feet for the height of 

 many of these mountains in the Eocene period. 



Volcanic activity is so often an accompaniment of eleva- 

 tion that we are not surprised to find that it was rife 

 throughout the whole of this region, and that great out- 

 pourings of basaltic lava occurred not only in Ireland and 

 Scotland, but in the Faroe Islands on the line of connec- 

 tion above-mentioned, as well as in Iceland and Green- 

 land. The denuded stumps of some of the great volcanoes 

 which existed at this time are found in Skye, Mull, Bum, 

 St. Kilda, and Ardnamurchan. The volcanoes of Skye 

 and Mull appear to have been on a grander scale than 

 the modern volcanoes of Italy ; Professor Judd estimates 

 that the base of the Mull volcano must have been at least 

 forty miles in circumference, and as Etna, from a base of 

 only thirty miles in circumference, rises to a height of 

 10,900 feet above the sea, he argues that if there was a 

 similar relation between the base and the altitude of the 

 Eocene volcano, the latter must have had an elevation of 

 at least 14,500 feet. Checking this by another calculation, 

 founded on the inclination of the lava-beds, he finds that 

 it could not have been less than 10,000 feet high. 



The existence of valleys, watercourses, and river-beds 

 among these Eocene lavas proves the country to have been 



