672 Professor George Chrystal [May 17, 



there in perfectly calm weather can ever forget the economic trans- 

 mission of energy by the long Pacific swell. Next to the transmission 

 by the ether of energy from the snn, this has always seemed to me 

 one of the most wonderful things in nature. 



Origin of Seiches. — The question of the origin of seiches is one 

 of great interest, on account of its connection with meteorology. It 

 abounds, however, in unsettled questions, which could not profitably 

 be discussed within the compass of a single hour. Moreover, the 

 data we have obtained are not yet fully discussed and ready for 

 publication. I will therefore be content with a few notes, the object 

 of which is to draw your attention to the interesting questions involved, 

 and to invite the assistance of any enthusiast present in the attempt 

 to solve them. 



Apart from obviously accidental causes, such as landslips, sudden 

 floods, etc., and causes such as earthquake disturbances, which have 

 not been proved to be other than accidental, the main causes of seiches 

 which have been indicated by Forel and his disciples are — 



1. The sudden release of a static denivellation of the whole lake 

 surface, caused by a barometric gradient along the lake, which has 

 suddenly been altered. 



2. The action over portions of the lake surface of small fluctua- 

 tions of the barometric pressure, which happen to synchronise with 

 one of the seiche periods of the lake. 



3. Action, similar to the last, of fluctuations in the velocity and 

 pressure of the wind, as shown in the anemogram. 



4. Sudden disturbance of a considerable portion of the lake surface 

 by the passage of squalls. This disturbance might be of a static 

 character, i.e. due to sudden increase or decrease of the barometric 

 pressure ; or it might be of a dynamic character, i.e. due to impact 

 of wind-gusts or rain-showers ; or, indeed, partly static and partly 

 dynamic. 



Clearly it is only by an induction from a large accumulation of 

 observed facts that we can hope perfectly to disentangle the action of 

 several of these causes, and assign to each its proper share in the origin 

 of seiches. We may notice, however, that the first and last mentioned, 

 which we may class as Sudden Disturbances, might be expected, in 

 general, to produce a sudden alteration in the limnogram ; while the 

 second and third, which we may class under the general name of 

 Resonance Disturbances, would, in general, give rise to a gradual 

 alteration. 



That both of these cases are actually observed I now proceed to 

 show by a few examples. In each slide you will see the limnogram, 

 the microbarograms at Ardtrostan, Lochearnhead, and Killin (which 

 is, roughly, about as far north of Lochearnhead as Ardtrostan is east 

 of the same spot), and also the anemogram taken at Ardtrostan. 



The limnograms at St. Fillans were all taken by the waggon 

 recorder. 



