328 On the Geological History of Loch Lomond. 



that and tlie Clyde, has been formed by the debris from the ele- 

 vations on the north, and the alhivial deposits tVoin the river on 

 the south ; that the tide at a former period has flown to the 

 head of Loch Lomond, as it now does to that of Loch Long and 

 Gair Locli; and that at that period Dumbarton Castle must have 

 been surrounded and standing in deep water, rearing its basaltic 

 mass above the circumambient element, like the Bass or Isla; — ■ 

 that the flat ground round the castle, that on which Dumbarton 

 now stands, with all the low grounds east of the Leven, extend- 

 ing from Dumbuck to Stonefteld, with the crofts of Dalquhurn, 

 Cordale Dillychyp, Bonhill, &c. with all the lower grounds round 

 that part of the lake where the Leven escapes from its bosom, 

 debouching towards the sea, owe their present elevation above 

 the Clyde, to tlie stones, gravel, and other alluvial matter brought 

 down and deposited by the river Endrick, which discharges itself 

 into the mouth of the present loch. So long as the abyss of the 

 lake continued to receive the deposits of the Endrick, no alter- 

 ation could take place on the surface of its waters ; which must 

 have then extended in one sheet of beautiful expanse, from the 

 Clyde to the head of the present lake, and from Dumbiuk on the 

 east, to the head-land on the west of Dumbarton bridge. But 

 after tbe accumulated matter from the Endrick rose to the el§;- 

 vation of the high water level, the lake getting brimful! every 

 flood tide, there would then, as far as the slender state of the 

 primitive but increasing barrier could oppose resistance to the 

 weight and pressure of the collected waters, be a torrent occa- 

 sioned at every ebb, which would carry along with it the mud, 

 clay, sand, gravel and stones, till the succeeding tide catching 

 the waters of the Leven like a thief loaded with the spoils of the 

 Endrick in its progress round the south head-land, would throw 

 the Leven with its alluvial treasures on the opposite shore, where 

 its stream would be impeded by the hill of Dumbuck ; and in 

 rounding westward to join the Clyde, the castle rock would op- 

 pose its stately resistance, to prevent the robbery and stilling th^ 

 waters, or give time for the lighter alluvials to deposit and settle 

 down; so that the first formation of alluvial soil must have been 

 in that water. The continual gatherings, the wreck of other 

 soils brought down by the Endrick, increased by every autumnal 

 torrent and winter flood, would collect and heap up from time to 

 time, till the waters thrown back upon the lake would accumitlate 

 such weight as to force the augmented, but still loose and un- 

 consolidated materials of its dam, forward into the vale belovv; till 

 the rushing water coming to its level, would lose its pressure and 

 allow the heavier matter to settle down, still carrying the lightep 

 substances on towards the Clyde, and lodging them behind the 

 castle rock. This in process of time vvonld bring that part to 



