of Edinburgh, Session 1885 - 86 . 
437 
fine but stout muslin, about 3 feet long and 1 foot diameter at the 
mouth, tapering to a cone in the bag. The mouth was kept open 
by a stout iron ring, which was made fast to the sounding line 
which passed diametrically across it. The water was of so clear 
and transparent a blue that it could be distinctly seen down to a 
depth of 1 9 fathoms ; and, with a weight of 1 4 lb. at the end of the 
line, it set itself perfectly steadily and almost rigidly in its direction. 
The results of the observations of the current at the surface on 
21st October 1883 were — 
Hourp.M., . . . 2.15 2.40 3.30 4.6 
Direction (true), . . 1ST. 11° E. N. 41° E. N. 56° E. 1ST. 101° E. 
Rate, knots per hour, 0*47 0’30 0*26 0*30 
It will be seen from these observations that, in the two hours, the 
current had shifted its direction through 90°, and had passed 
through a minimum velocity of 0'’26 per hour without there having 
been any period of “slack water.” The observations are too few in 
number to make it worth while submitting them to analysis, but 
a little study of them will show that they indicate a current 
which is the resultant of a constant current and a periodic one. 
A constant current running to S.E. by E., combined with a tidal 
current running bT.N.W. and S.S.E., the maximum velocity of 
which, in either direction, is twice that of the permanent current, 
would give a resultant current agreeing fairly with that observed. 
Under these circumstances, the path of a particle, floating freely in 
the water and moving with the water, would describe in twenty-four 
hours a path having the shape of the letter S, the larger axis of 
which has a bf.W. by W. and S.E. by E. direction. If the tidal 
current be supposed to have motion in an elliptical orbit, instead of 
a simple oscillation in one direction, the path in the twenty-four 
hours would take some such form as the figure 3. Without insist- 
ing further on the numerical value of the results, the observations 
are of importance as showing decidedly the existence of tidal 
currents in the open ocean. Amongst the islands of the Canary 
group these currents are strongly developed. Between Grand 
Canary and Teneriffe the channel is broad, and, at its shallowest 
part, over 1000 fathoms deep ; yet the tidal current reaches to the 
very bottom, and its scouring action is shown by the nature of the 
