208 PROCEEDINGS OF THE GEOLOGICAL society. ([Jan. 5, 
to classify aright these Scottish rocks and assign them their true 
position in the great series of Paleozoic formations now so ably and 
fully wrought out in the sister kmgdom. 
In conclusion, I would thus sum up the series of geological events 
in this region, which are attested by existmg phenomena. At the 
earliest period of which any indication remains, this district was a 
portion of a deep sea, into which detritus of quartzose and argil- 
laceous rocks was conveyed, and spread out by currents probably 
from the north. In some parts of this ocean animals existed in con- 
siderable abundance,—graptolites and soft fleshy animals where mud 
prevailed ; encrinites, orthide and trilobites where more calcareous 
matter was to be found, and probably near the foci of igneous action. 
After a thick mass of strata had been deposited some power has 
pressed these beds together to huge longitudinal folds, and raising 
them above the sea put a stop to the succession of deposits. At the 
same time it would appear that the ves of felspar porphyry were in- 
jected among these beds, hardening the whole mass and more highly 
modifying particular portions. By means of aqueous agents the 
formation was then cut into a system of hills and valleys, the eroding 
action of course being directed chiefly along the lines of fracture 
caused by the elevation of the mass. A depression of the land must 
next have taken place when the sea flowed up the valleys and de- 
posited the red sandstone strata in them and around the shores of 
the greywacke islands. Durmg the whole of the old red sandstone 
and carboniferous periods, but slight physical changes seem to have 
occurred in this portion of Scotland. At the close of the latter, 
however, there has been a great eruption of igneous rocks, forming 
the chains of the Pentlands on the north, and the Chevicts on the 
south. Itis evident from the relation of the porphyries forming 
these mountains to the red sandstone, that they are more recent than 
this deposit. The augitic trap rocks scattered throughout the 
secondary formations in the Lothians on the north, and Roxburgh 
and Berwickshire on the south, seem of still more recent date than 
the porphyries, and probably were conjomed with an elevation of the 
land, which brought the whole of the secondary deposits in the 
south of Scotland to a close. No trace of any of the recent secondary 
formations or of any of the earlier tertiary deposits has certainly been 
observed in this tract of country. Its geological history is almost an 
entire blank till the diluvial epoch, when there is evidence that the 
whole district, even to the summits of the highest mountains, 2000 
feet above the sea, has again been under water. But neither this im- 
mersion of the land in the ocean, nor its subsequent elevation, appear 
to have been connected with any important change in its general 
character or physical outline. The boulders of primary rocks from 
the Highlands, and of trap rocks from the west coast, especially the 
very characteristic zeolitic traps of Dumbartonshire, which are by 
no means rare in the valley of the Tweed, together with the general 
distribution of the superficial deposits, prove that no great change 
in these respects can have taken place. Except the gradual erosion 
and denudation of the superior beds, which has in many places left 
