SEICHES AND OTHER OSCILLATIONS 
79 
We have already given incidentally some examples of the 
effect of a periodic disturbing agency, and shall now add a few 
more. 
16th September. — About 6^ (see fig. 29) a succession of four very 
regular waves of barometric disturbance, having a period of 13 "3™, 
^ui/Ajy^flwn /d q OS. 
Fig. 29. 
generated a very regular UB-dicrote, which lasted about 15'\ 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 
16 
17-9 
4-1 
„ 21 
9-8 
4-2 
16?^/? October^ 4'^-9^ (see fig. 21, above). — A very interesting 
example, showing both positively and negatively the effect of a 
periodic barometric disturbance, is obtained by contrasting the 
limnograms taken simultaneously on Loch Tay at Killin, and on Loch 
Earn at Lochearnhead. The period of the microbaric disturbance is 
about 29"^, and it will be observed that it greatly increases the uni- 
nodal seiche of Loch Tay, the period of which is about 28-4™. 
Indeed, the uninodal thus produced was the best found on Loch 
Tay. On the other hand, this strong barometric disturbance produces 
little or no effect on the smooth UB-dicrote which was in progress 
on Loch Earn, because the periods of its components are 14 "52™ 
and 8-09"^. 
^5th October^ 3^^- 8^ (fig. 30). — Microbaric disturbances of period 
7-5"^ to 8-0"^ brought out the binodal of Loch Earn (T2 = 8-09'") and 
the quadrinodal of Loch Tay (T^ = 8-6"^). 
