18 ANNIVERSARY ADDRESS. 
I am here assuming that the storms there are of the same 
character as those which pass over Sydney, but they may be 
smaller when passing the lake, and travel more slowly. Certainly 
the storm which I saw coming down the lake did not travel with 
anything like such velocity. M. Vaucher, who studied for years 
motions of the same kind which take place in the Lake of Geneva, 
considered himself justified in saying—‘The lake is disturbed 
when the barometer is unsteady; and because of the varying pres- 
sure.” From what I have seen so far, the first part of this is true 
of Lake George, but it is not because the barometer is unsteady, 
but because at such times the wind is puffy and variable, and 
imparts to the water its own peculiarity. Of the power of the 
wind to set the water in motion I have mentioned several instances 
to-night, which I need not repeat, but I may add that the large 
impulses come from the north because, as it seems to me, the wind 
from that direction acting on the water the whole length of the 
lake has greater power than when blowing from the south over a 
mile of water. The gauge is fixed about a mile from the south end. 
But although the wind is such an obvious cause of the phenomena 
under discussion, I think the barometric changes have some share 
in it, and there are some changes recorded which, so far, I am 
unable to refer to any cause. 
In the European lakes, in addition to the changes of level due 
to rain and evaporation, there are other changes of level indepen- 
dent of these causes, and which resemble tides in their rhythmic 
periods. These have long been known and observed in Switzer- 
land, and especially on the Lake of Geneva, where they are known 
by the name of “seiches.” When they affect the lake its level is 
observed to rise slowly during thirty orforty minutestoa height that 
varies from a few inches to as many feet ; it then falls again slowly 
to a corresponding depth, and so on. These seiches have been 
studied for many years, and M. Vaucher said that he had observed 
that “ when the barometer was at rest the seiches were small, are 
greater when the barometer is variable, and greatest when the 
pressure is falling.” A seich is defined as a complete motion of 
