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XXV.—On the Hydrodynamical Theory of Seiches. By Professor Chrystal. 
Wir A BIBLIOGRAPHICAL SKETCH. 
(Read June 19, 1905. Issued separately July 3, 1905.) 
PARE 
GENERAL SUMMARY.* 
§ 1. The variations of the surface-level of lakes due to the direct action of wind and 
rain, and the smaller disturbances caused by surface waves, of small or moderate length, 
due to the action of the wind and the movement of boats and animals, must have been 
familiar phenomena at all times. The first accurately recorded observation, that lake- 
levels are subject to a rhythmic variation, similar in some respects to the ocean tides, 
seems to have been made at Geneva in 1730 by Fatio pe DurILuer, a well-known Swiss 
engineer. Owing to the peculiar configuration of the Geneva end of Lake Léman, 
these variations occasionally reach a magnitude of 5 or even 6 feet; and DvuILLIER 
mentions that they were known in his time by the local name of “‘ Seiches,” which has 
now been applied to rhythmic alterations of the level of lakes in general. 
From Duiuurer’s time onwards various observations and speculations regarding the 
seiches of Lake Léman are recorded. It seems to have been J. P. EK. Vaucuer, Pastor, 
and Professor successively of Botany and Church History at Geneva, who, in a memoir 
written between 1802 and 1804, and published in the memoirs of the Physical Society 
of Geneva in 1833, first pointed out that seiches are not confined to Léman, but are 
to be found more or less in all lakes; that they may be of all degrees of amplitude up 
to 5 feet; and may occur at all seasons of the year, although their occurrence seems to 
be affected by the state of the atmosphere. He also pointed out that the amplitude 
of the seiches in Léman increases towards its western end; and that the seiches at 
its eastern end are not more marked than those observed in other lakes. 
These and other early observations of seiches are mentioned by Foret in his great 
monograph on the Lake of Geneva, vol. ii. p. 50. In particular, he cites one observed 
at Kenmore on Loch Tay in 1784, which lasted several hours, and is said to have had 
a period of seven minutes and a maximum amplitude of nearly 5 feet. 
A still earlier example is given in the Scots Magazme for 1755, p. 598, from which 
it appears that seiches were caused in several of the lakes of Scotland by the great 
earthquake of Lisbon on 1st November 1755. 
As the source is not easily accessible to everyone, an extract may be printed here :— 
* For the convenience of those who are more interested in the observation of seiches than in the purely mathe- 
matical theory, I have separated the mathematics, so far as possible, from the general statement of the conclusions 
arrived at and the suggestions of further problems to be solved by experiment or observation. 
TRANS. ROY. SOC. EDIN., VOL. XLI. PART III. (NO. 25). - 89 
