Birge—On the Evidence for Temperature Seiches. 1011 
In like manner may be seen that all of the considerable 
rises of temperature in the deeper water of Loch Hess during 
August were preceded or accompanied by a northeast or on¬ 
shore wind. The relation is plain in the movement of Aug. 
15, as is shown on the diagram. The similar movement of 
the isotherms on the night of Aug. 22-23 coincided with an 
on-shore wind. The same is true of the movements on Aug. 
11 and the night of Aug. 19-20, although they need separate 
discussion. The decline of temperature at a depth of 50 feet 
on Aug. 8, referred to as a seiche by Wedderburn (’07, p. 
422) was accompanied by southwest or off-shore wind and by 
a fall of surface temperature certainly due to this wind. The 
similar drop of temperature at 50 feet on Aug. 14, also re¬ 
ferred to by Wedderburn, coincided with a shift of wind from 
northeast to southwest and the temperature rose again when 
the wind turned, at 10 p. m., to the northeast. Thus every 
considerable shift of temperature in and below the thermocline 
during August was precisely that which might have been pre¬ 
dicted as probably resulting from the meteorological changes; 
the position of the observing station and the direction of the 
wind being known. So far from the evidence showing that 
these major oscillations are independent of changes in the 
epilimnion, they coincide with such changes and with mete¬ 
orological forces directly adapted to cause them. 
I do not mean to say that we are able thus to account for 
every chang'e of temperature at every depth in this series of 
observations. We are ignorant of the underwater currents in 
Loch Hess, and of the minor effects of the winds; and their 
major effects are matters of inference rather than of observa¬ 
tion. We know that these effects are numerous and complex. 
When a mass of warm water is once established at the lee end 
of a lake it often shifts and moves about in an irregular and 
quite incalculable fashion. It is acted upon by numerous 
forces, each quantitatively unknown, including not only wind 
currents but convection currents, as well as underwater cur¬ 
rents set up in the past, and the numerous and doubtful inter¬ 
actions between this warm mass and the cold outer water 
crowding in upon it. But if seiches are to be asserted as the 
