Progress of the Geological Survey of Scotland. 131 



most important components being those bituminous shales from 

 which oil is now so extensively obtained. In the east of Fife it 

 contains a great many bands of Limestones, having the fossils and 

 general aspect of true Carboniferous Limestone beds, while in Ber- 

 wickshire it reassumes the aspect which it shows in Ayrshire and 

 the west. 



An important feature in the recent work of the Survey is the 

 mapping of the Permian basins of Ayrshire and Thornhill, and the 

 discovery of a beautiful series of contemporaneous igneous rocks as- 

 sociated with the Permian sandstones of both these localities.^ 



In connection with this subject, Mr. Geikie remarked that the 

 detailed labours of the Survey had now brought to light the history 

 of a long, though interrupted, series of volcanic phenomena, dating 

 from the time of the Lower Old Red Sandstone, and extending even 

 into the Tertiary period. Of these igneous rocks, the oldest group 

 forms the range of broken hilly ground, which stretches from near 

 Edinburgh south-westward through Lanarkshire, into the south of 

 Ayrshire. The next series, in point of age, is that which belongs 

 apparently to a middle division of the Old Eed Sandstone, and 

 forms the hills to the south of the town of Ayr. Then come indi- 

 cations of volcanic activity in the Upper Old Red Sandstone of the 

 east of Scotland. The earlier half of the Carboniferous period in 

 Scotland, was marked by the abundance and activity of the 

 volcanos. The remains of the lavas and ashes then erupted form 

 the hills in the north of Ayrshire and Renfrewshire, and most of 

 the craggy hills which roughen the area of the Lothians and of Fife. 

 Next in order of time are the interesting traces of volcanic action 

 associated with the Permian rocks of Ayrshire and Nithsdale, which 

 will be described in a forthcoming portion of the Memoirs of the 

 Geological Survey. The most recent igneous rocks yet traced are 

 dolerite-dykes, which run across all the other rocks and even cross 

 large faults without any deviation. These Mr. Geikie believes to be 

 connected with the great dolerite plateau of Antrim and the western 

 islands, and to be of Miocene age. 



Several areas of Metamoi'phic rocks have been mapped in detail, 

 particularly by Mr. James Geikie, and the gradual passage of 

 different stratified rocks into crystalline porphyries and granite rocks, 

 has been traced both in the Lower Silurian and the Lower Old Red 

 Sandstone districts. 



The mapping in of the superficial deposits has been steadily pro- 

 secuted along with the survey of the rocks underneath. Particular at- 

 tention has likewise been bestowed upon the traces of ice-groovings, 

 and it will, probably be possible, before many years are gone, to shew 

 on a map, and in some detail, the movements of the great ice-sheets 

 of the Glacial period. While these researches are advancing, atten- 

 tion is necessarily drawn every day to the connexion between the 

 external form of the ground and the structure of the rocks below. 

 A mass of evidence has now been accumulated by the Geological 

 Survey, to show that, as was originally maintained by Hutton, the 

 1 See Geol. Mag. Vol. III. p 243. 



