I 



On the Geological History of Loch Lomond. 329 



the level of the highest tide. The new-made soil would soon be 

 furnished with the seeds and many of the roots of the various 

 plants indic;enous within the whole range of the lake, the Clyde, 

 and all the tributary streams. Reeds, rushes, and other vege- 

 tables would soon cover the surface, and add rapidly to its ele- 

 vation; in cases of autumnal floods filtering the water as it passed 

 to the sea, and retaining the slush, not only of the river, but in 

 a more eminent degree that of the land-rills and hill- burns, 

 raised by occasional thunder-plumps and other heavy rains, 

 winter freshes and storms, which must have brought down great 

 quantities of soil and debris from their kindred heights, and given 

 birth to the gradual and gentle inclination towards the rising 

 ground, which now hides from human eyes all marks of their 

 origin and former state. After the quantity of matter at the 

 mouth of the lake had equalled the ordinary level of the highest 

 tides, and acquired a solidity beyond the elevated pressure of the 

 water during the recess of the sea, there were still great efiorts 

 to be made to bring the surface of the lake to twenty-two feet 

 of altitude, and the whole vale of Leven, from the castle to the 

 lake, to a gently inclined plane. This must have been the work 

 of time, and a succession of heapings and leveiings before the loose 

 materials had gained that compact solidity to present an effectual 

 resistance ; even after the dam had accjuired a consistency and 

 durability sufficient to repel the effects of any ordinary flood, the 

 grand finishing strokes given to this fairy-land must have been 

 the effects of a succession of winter freshes, after severe and 

 lengthened storms and frosts. The vast surface of the lake l)eing 

 covered with ice of great strength and thickness, and swollen by 

 the mountain t«rrents above its usual heiglit, the accumulated 

 ice would of itself become an elevated and powerful obstruction 

 to the di-^charge of the surplus waters ; till overcome by the in- 

 creasing weight, it would sweep from bank to brae, tearing up 

 and leveling every thing before it, carrying from round the 

 edges of the lake and the islands, and still more from its newly- 

 formed dam, great quantities of stones, gravel, fragments of 

 rock. Even blocks of great size firmly fixed in the ice, might 

 jn this way have been floated down, till grounding somewhere, 

 they remained, or dropped into the hollows by the melting or burst- 

 ing of the crushing ice dashed against the rocks of either shore. 



The shoals of herrings that abound in Loch Lomond have been 

 adduced as a proof, that the obstruction of the original commu- 

 nication between the lake and the sea must have been the effect 

 of some sudden convulsion : but that idea proceeds from the pro- 

 pensity that many people have to account for every change by 

 something strange and marvellous, williout deigning to look into 

 or inquire after the unceasing progress of nature in her most legi- 

 timate 



