670 



Professor George Ghrystal 

 Peeiods op Loch Earn. 



[May 17, 



the two others show its uniuodal and binodal components nearly pure, 

 because they were taken simultaneously with the first, near the com- 

 puted places of the binode and uninode respectively. 



The next picture (Fig. 10) gives a comparison between simul- 

 taneous seiches on Lochs Earn and Tay, which you will remember are 



Fig. 9. 



not very far apart. The distance between their western ends is 6i 

 miles. Tay is more than double the length of Earn, but only about 

 50 ft. deeper. It is therefore relativelya shallower lake. It is curious 

 to notice how variable the seiche is on Tay as compared with Earn, the 

 two pieces of limnogram from the latter being parts of the long seiche 

 of 6 1 days which I have mentioned before ; and yet the first of the 

 two pieces from Tay is the purest example of a uniuodal that we got 

 from Tay during more than two months' observation. 



