314 
Proceedings of the Royal Society of Edinburgh. [Sess. 
of the waves will be necessary. The present observations are, however, 
sufficiently accurate to show the general nature of currents in the loch. 
An attempt was made to carry out our previous suggestion of numbering 
the balls which indicate the direction of the current, so as to determine how 
the direction of the current varied. This was found quite workable, and it 
showed that the variation in direction was very irregular, and was not due 
to a gradual change of direction. As an example, the following observation 
at 45 feet on 6th August may be cited. The observation lasted for one 
west East 
hour, and during that time the average rate of the^current was 4’5 centi- 
metres per second. There were eleven indications of direction, and the 
following is the manner in which the^direction varied : — 
1st indication, N. 60° W. 
2nd 
„ N. 80° W. 
3rd 
„ N. 70° W. 
4th 
„ w°. 
5th 
„ w°. 
6th 
„ N. 60° W. 
7th indication, S. 80° W. 
8th 
„ S. 60° W. 
9th 
„ S. 50° W. 
10th 
„ N. 80° W. 
11th 
„ S. 40° W. 
The numbered balls were troublesome to work with in stormy weather 
and consumed a good deal of time, so that after the irregularity of the 
variation in direction had been ascertained, ordinary unnumbered balls 
were used. 
There was a well-marked temperature discontinuity in the lake during 
