SEICHES AND OTHER OSCILLATIONS 
83 
there is some reason to believe thai" in part at least they reflect in 
miniature the action of the causes which produce the storm-waves 
of the ocean, our knowledge of which is still far from complete, 
although they are of such vital importance to seafaring men. 
Inasmuch as our first object was to determine as accurately as 
possible the seiche-periods and the positions of the nodes of Loch 
Earn, the limited time at our command was allotted and our apparatus 
disposed mainly for these two purposes, and it was not until near 
the end of our observations, after the extemporisation of the stato- 
limnograph, that much attention was given to the vibrations of the 
lake. We cannot, therefore, pretend to offer much towards a final 
solution of the problem of the vibrations ; but we may record a few 
observations which seem to enhance the interest of the question, and 
may ultimately prove useful in its final solution. 
The embroidery caused by these vibrations, as may be seen by 
studying some of the figures in this article, varies considerably in 
form, and may be regular or irregular according to circumstances. It 
must also be remembered, as was long ago pointed out by Forel, 
that, owing to the damping effect of the well and access tube, each 
limnograph reproduces more or less of these vibrations according to 
its adjustment. The statolimnograph, used with a wide access tube, 
owing to the very small inertia of its moving parts, is best adapted 
for this purpose. 
Although occasionally the embroidery continues regular for a 
considerable time, and appears to have a perfectly definite period 
and constant or at least slowly varying range, as a rule its configura- 
tion changes rapidly, and any regularity is transient. This makes 
it very difficult to analyse it into harmonic components, even if 
analysis into a finite number of such components were possible. 
In our observations the maximum range of the vibrations varied 
from 0 to 21 mm. ; an average value might be about 6 mm. At 
times the range of the vibrations {e.g. fig. 33) exceeded the range of 
the seiche, so that the former quite obscured the latter. 
The periods observed showed much less variation. In the limno- 
grams taken with the waggon recorder and Sarasin instruments, the 
period ran from 1 '3™ to 2™ ; in the statolimnograms, from -42"^ to 
•79™. It must be remembered, however, that in the latter the short- 
period embroidery obscures that of longer period, and in the former 
the vibrations of shortest period are damped out. For the ordinary 
limnograms the average of the periods might be put at 1'47"\ The 
period that actually occurred oftenest in the cases examined was 1*5™. 
The embroidery was never observed unless there had been sufficient 
wind to cause progressive surface waves, and it subsided at once when 
these waves disappeared. The observations of Halbfass, Endros, and 
