72 
THE FRESH-WATER LOCHS OF SCOTLAND 
The result would therefore be a .seiche having a range of 46 mm. It 
will be noticed that the effect arising from the impact, viz. '036, is 
negligible. 
The conclusion thus arrived at bears out the inference of Endros ^ 
regarding the effect of a rainfall of 7 mm. during 20™ upon the 4S™ 
seiche of the Chiemsee. Such a fall on one half of a parabolic lake 
having a 40™ period would generate a uninodal seiche having a range 
of 10*5 mm. 
There is little doubt that in some of the cases, to be cited 
presently, the precipitation played an important part ; but the 
observations of Shaw and Dines on the effect of passing rain-clouds 
in raising the barometric pressure tend to place difficulties in the way 
of separating the effect of precipitation from the barometric pressure 
proper. It would appear that the pressure to which the lake reacts 
so delicately is equal to the pressure before the rain has fallen — that 
is, while it is still in the cloud in the form of vapour ; but the matter 
requires and deserves further investigation. 
5. Effect of Squalls.— On 11th August, 8^^ to 9^^ a prolonged 
depression on the microbarogram is associated with a prolonged 
elevation on the limnogram. The release of this denivellation caused 
a considerable uninodal seiche (see fig. 25). 
On 7th September, about 8'^ 30™, occurred the greatest barometric 
fluctuation of short duration observed."^ The extreme range was 
19'3 mm. (Aq.), the total duration about half an hour. It came from 
E. 56° N. with a velocitv of propagation of 19 (mile/hour), the velocity 
along the lake being about 30. 
As will be seen from fig. 26, the effect was to increase the total 
range of the seiche from about 18 mm. to 50 mm., and to generate a 
strong BT-dicrote. It is worthy of remark that the rise in the wind 
follows about an hour after the barometric disturbance. To the spiky 
anemogram which then follows corresponds a strongly embroidered 
seiche, which shows no increase in maximum range. I have tried, 
but unsuccessfully, to find a period in the anemogram corresponding 
to that of the seiche-embroidery, viz. T = 1'5™ to 1*6™. 
On 8th September, between 16^^ and 17^\ a well-marked barometric 
disturbance, having a range of 3 mm. to 4 mm. (Aq.), caused a change 
of phase in the previously existing UB-seiche, and also a considerable 
increase of range. This UB then persisted for nearly 24^, until about 
13^ 15™ on the 9th September its configuration was utterly destroyed 
by the great barometric disturbance shown in fig. 27. This disturb- 
ance lasted nearly two hours, and caused a maximum depression of 
14 mm. (Aq.); it came from W. 62° S. to W. 67° S., and travelled 
1 Seeschwankungen heohachtet am Chiemsee (1903), p. 103. 
2 For further details see my paper, Proc. Roy. Soc. Edm., vol. xxviii. p. 457. 
