1908-9.] Observations with a Current Meter in Loch Ness. 625 
f erred from one side of a node to the other is (as the node is at the centre 
of the lake) 1800000 x 2300 x 6 = 4145 x 10 7 cub. cm., where 6 is the breadth 
of the lake. All this water must pass through the nodal section, and it was 
assumed that in the upper and lower layers respectively this transference was 
accomplished by a current uniformly spread over the nodal section whose area 
in the upper layer is 466 x 10 2 sq. cm. and in the lower layer 926 x 10 2 sq. cm. 
The transference takes place in half the period of the seiche, which for purposes 
of computation was taken as forty hours. The average rate of the current 
at the node on the foregoing assumptions is, then, in the upper layer 
414 xlO 7 
46 x 10 2 x 40 x 3600 
cm. 
sec., or approximately 6 cm. sec., and similarly in 
the lower layer 3 cm. sec. The currents in the two layers are of course in 
opposite directions. If it is further assumed that the motion of the water 
particles is harmonic, the maximum velocities of these currents are found to 
be about 10 cm. sea and 5 cm. sec. respectively. A current of 10 cm. sec. 
would produce over 20 revs, per minute of the propeller of the current meter. 
In the tables of observations in the Appendix, the first entry gives the 
rate of the current in centimetres per second calculated according to the 
formula supplied with the instrument. The second entry shows the 
directions of the current. The prefix gives the number of balls which have 
fallen into the compass box, and the suffix the variation of the directions in 
degrees. The centre figure gives the number of degrees east or west of 
north or south which denote the mean direction for the current. The third 
entry gives the time of commencing and sending the observation in hours 
(numbered from 1 to 24) and minutes. A bar over the time of ending the 
observation indicates that the observation was not ended until the next 
day, and that the hour refers to the following day. At the top of each 
column appears the date on which the observation was commenced, and at 
the left hand the depth at which the observations were made are shown. 
Thus the entry for 150 feet on 12th August: T2 12 N7E 1S0 17*32 — 10’28, 
means that the average velocity for the currents for the period of observa- 
tion was 12 cm. secs. ; that there were twelve indications of direction, that 
the average direction was 7° east of north, that the variation in the 
direction of the current was 180°; that the observation started at 17 hours 
(5 p.m.) 32 minutes on the 12th and ended at 10 hours 28 minutes on 13th 
August. 
All temperatures are measured in degrees Fahrenheit, and all depths 
are given in feet. Wind force is estimated on the scale 1 to 10. 
A glance at the tabulated observations will show the great complexity 
of the results and will give some idea of the difficulty of correlating them. 
VOL. xxix. 40 
