1907.] Seiches in the Lakes of Scotland. 65' 



AVEEKLY EVENING MEETING, 



Friday, May 17, 1907. 



His Grace The Duke of Xorthoiberlaxd, K.G. P.O. D.C.L. 

 F.R.S., President, in the Chair. 



Professor George Chrystal, M.A. LL.D. Sec.R.S.E. 



Seiches in the Lakes of Scotland. 



Historical Introduction. — As my subject to-night is Seiches in the 

 Lakes of Scotland, I could scarcely begin better than by quoting the 

 following extract from the ' Scots Magazine ' for 1755, which gives a 

 good general account of the phenomenon called a seiche, and is the 

 earHest accurate account that I know of any such thing in Scotland : — 



" On the first of November last, Loch Lomond all of a sudden, 

 and without the least gust of wind, rose against its banks with great 

 rapidity : and, immediately retiring, in about five minutes subsided as 

 low, in appearance, as ever it used to be in the greatest drought of 

 summer. In about five minutes after it returned again, as high and 

 with as great raj^idity as before. The agitation continued in the same 

 manner, from half an hour past nine till fifteen minutes after ten in 

 the morning ; the waters taking five minutes to subside and as many 

 to rise again. From ten to eleven, the agitation was not so great, and 

 every rise was somewhat less than the immediately preceding one, but 

 taking the same time, viz. five minutes to flow, and five to ebb as 

 before. About eleven the agitation ceased. The height the waters 

 rose was measured immediately after, and was found to be 2 feet 

 6 inches perpendicular. 



" The same day, at the same hour. Loch Lung and Loch Keatrin 

 were agitated in much the same manner ; and we are informed from 

 Inverness, that the agitation in Loch Ness was so violent as to threaten 

 destruction to some houses built on the side of it." 



From this clear account there can be no doubt that the phenome- 

 non described was a seiche, catised by the great earthquake which 

 destroyed Lisbon on the morning of November 1, 1755. In two im- 

 portant respects this seiche is, however, exceptional. Its amplitude, 

 i.e. the rise of the water above the ordinary level, is much out of the 

 common, and, so far as we know, ordinary seiches, which are plentiful 

 enough, are very rarely caused by earthquakes, although earthquakes 

 of small amphtude are of everyday occurrence, as any seismologist 

 will tell vou. 



Vol. XTIII. (No. 101) 2 u 



