486 



PROFESSOR CHRYSTAL 



§» 



= 



duces a UBT-tricrote seiche. This was the best example obtained during our 

 observations. 



Uh September, h -8 h . — Fig. 14 shows a case where a strong trinodal component 

 was introduced into a UB-dicrote by microbaric disturbances having periods of 6T", 

 8-0™, 8-2 m , 5-l m 



6th September. — From 2 h to 10 h there was a perfectly smooth UB-dicrote, part of 

 which is reproduced in fig. 4, vol. xlv., p. 366 of the Transactions. At first the 

 uninodal component decreases and the binodal increases. Thus, at 3 h , 2U = 117 mm., 

 2B=13"3 mm.; at 5 h 30 m , 2U = 3'9mm., 2B=15mm. The microbarogram shows 



J 



CM 



fl/icLfriOi-tam j* qos 



McyrwcPci/nt ffos 



s 



7 



S-CM 



O.Hj? 



Fig. 14. 



S 



6 



7 



periods of 107 m about 4 h , and 9*4 m about 6 h , which were no doubt responsible for 

 this gradual alteration of the seiche. 



16^ September. — About 6 h (see fig. 15) a succession of four very regular waves 

 of barometric disturbance, having a period of 13'3 m , generated a very regular UB-dicrote, 

 which lasted about 15 h . The uninodal component gradually diminished, as will be seen 

 from the following measurements : — 



Hour. 



2U. 



2B. 



h. 



mm. 



mm. 



Ca 10 



22-9 



4-5 



,, 10 



17-9 



4-1 



„ 21 



9-8 



4-2 



16</i October, 4 h -9 h (see fig. 2, above). — A very interesting example, showing 

 both positively and negatively the effect of a periodic barometric disturbance, is 



