TEMPERATURE OF SCOTTISH LAKES 
127 
in July 1908, and an oscillation with a period of about twelve hours 
can be traced. This period also agrees wonderfully with the period 
calculated from the formula given above. 
The amplitude of the oscillation is sometimes enormous. In Loch 
Ness an amplitude of nearly i200 feet was observed in August 1904, 
Fig. 49. 
which is, of course, far greater than any amplitude which could occur 
in an ordinary seiche. 
The period of the temperature seiche, as will be seen from the 
formula, varies according to the difference in temperature and the 
depths of the upper and lower layers. As the autumn progresses the 
difference in temperature between the layers diminishes, the depth of 
the upper layer increases, and the depth of the lower layer decreases. 
