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Proceedings of the Royal Society of Edinburgh. [Sess. 
only 1(H) cm. sec., and that was a return current at the surface, setting in as 
a S.W. gale died away. At the more sheltered position at Invermoriston 
velocities were registered up to 17 cm. sec. on several occasions, and in a con- 
siderable number of cases there were observations of velocities exceeding 10 
cm. sec. The slowness of the currents is probably due to the proximity of 
the head of the lake and to the shallowing of the basin, for there must 
obviously be at each end of a lake a certain amount of water which does not 
partake of the general circulation of the lake. 
The comparative shallowness of the water at Invermoriston may also, by 
confining the depth through which the currents could move, have increased 
their velocity ; but this is unlikely, as it is really the depth of the temperature 
discontinuity which determines the depth to which the currents descend. 
No velocity above 5 cm. sec. was observed below 120 feet, but at that 
depth there are two observations of a current velocity of 5 cm. sec., both 
during S.W. gales. Curiously, one was a direct current (10th October) and 
the other a return current (29th September). 
There are only observations on two days with N.E. winds from which 
reliable conclusions can be drawn, viz. 24th September and 15th October. 
On the former date the easterly current was decidedly felt at 180 feet about 
midday, but three hours later the return current has had time to set in, and, 
with practically the same velocity as the direct current had at 180 feet, it 
appears at 150 feet. On the 15th October, when the easterly wind had been 
blowing for not more than twelve hours, the return current is taking place 
steadily between 60 and 120 feet. On the following day the currents are 
again confused. There is a tendency for the return current to appear near 
the surface, while direct currents are also recorded at considerable depths. 
In consequence, there are indications of currents of all directions at 60 feet. 
Unfortunately in the other observations the compass needle was displaced. 
In spite of the variable conditions there are a sufficient number of 
observations taken on days when the currents were comparatively steady to 
warrant our drawing the same general conclusions as regards S.W. winds as 
at Invermoriston, viz., that the return current tends to appear very near 
the surface. The return current appeared at 30 feet on the 3rd, 7th, and 9th 
October, at 60 feet on 28th September and 19th October, and at 90 feet on 29th 
September. The observations on 7th October are especially clear. They 
show a S.W. current at the surface, a N.E. current from 30 to 120 feet, and 
a S.W. current at 300 feet. These observations strongly resemble the 
Invermoriston observations of 17th September in showing a deep water 
current in the same direction as the surface current. A similar observation 
made on 20th October, in which some method of distinguishing the order in 
