1907.] 



on Seiches in the Lakes of Scotland. 



/i) 



I observed that it suddenly stopped short about the middle of the 

 lake. It was afterwards found that the rain had not come east 

 of Ardvoirlich. The weather in the forenoon had been calm and 

 sunny, and the advent of the squall was quite sudden. This is well 

 seen both on the microbarograms and on the anemograms. One of 

 the Lake Survey staff was looking at the uninode limnograph, and 

 stated that he saw it record the sharp depression on the limnogram 

 just as the squall came up. For some time immediately before, the 

 limnographs at the uninode, binode, and at St. Fillans, had been 

 drawing almost straight lines. The seiche weather had, in fact, been 

 the calmest known in our two months of observation : so that we 

 caught the lake in the very act of responding to the storm. The 

 maximum depression at the uninode and the maximum elevation at 



i 



- Microbar. 



Anemogr. 



Fig. 16. 



the binode were nearly simultaneous, the latter apparently following 

 about Ij minute after the former. Unfortunately, owing to the 

 irregularity of the clock at the uninode, certainty on this point is 

 not attainable. 



It is however abundantly clear, that an elevation of the lake surface 

 travelled along the eastern part of the lake. The first rise occurred 

 at 13 hr. 55-31 min. at the binode ; and at 14 hr. 5* 24 min., i.e. 

 9 '93 min. later, at the Pic-Nic point. The first maximum elevation 

 is seen at 14 hr. 1'05 min. at the binode, and at 14 hr. 10 '57 min., 

 i.e. 9 '52 min. later, at Pic-Nic point. If the disturbance had 

 travelled as a solitary wave of sufficient extent to be treated as " long," 

 I calculate that it ought to have taken about 7 minutes to make 

 the journev in question. 



2x2 



