from the relative positions of the watch-buoy and the
log-ship; the actual movement of the watch-buoy
with reference to a fixed point will be the resultant of
the movement of the surface-water and the movement
of the watch-buoy through the surface-water. This
Avould he sufficiently simple if we could suppose th a t
the surface-drift has no influence upon the watch-
buoy and th at the movements of intermediate water
r ix o d poln' 100 fins Watchbuoy
^200 flits Watch buoy
.Scale of 5 Cables = | Mile
2 3
F io. 90.—Result of Current Observations made on th e 24th of April reduced to a
diagrammatic form.
do not affect the ‘ current-line ; ’ but we are well
aAvare th a t this cannot he the case, and as we have
no data for estimating the amount of error arising
from these sources, our current determinations can
as yet be regarded only as approximations. The
following table gives the results for the 24th of
April.
Hi
