274 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
minutes later than it is at Holyhead. For the south end 
of the Isle of Man about 14 minutes has to be subtracted 
from the Liverpool time, and high tide at the Isle of Man 
is synchronous with that at Dover. The tidal rise and 
fall at Liverpool varies from about 11 feet at low neaps, 
to 31 feet at high springs. All the highest tides in our 
district occur about midday and midnight, consequently 
the lowest spring tides, which are the best opportunities 
that the naturalist has for collecting marine animals on 
the shore, are about 6 a.m. and 6 p.m., an arrangement 
which allows of two tides a day being worked in summer, 
but prevents, on account of darkness, a low spring tide 
from being seen during the winter half of the year. 
There is some reason to believe that, as a result of the 
general drift of the surface waters of the Atlantic, and the 
shape and direction of the openings to the Irish Sea, more 
water passes out by the North Channel than enters that 
way, and more water enters by the South (St. George’s) 
Channel than passes back, and that consequently there is, 
irrespective of the tides, a slow current passing from south 
to north through our district. The fact that so many of 
our drift bottles have crossed the “ head of the tide ” from 
S. to N., and that of those which have gone out of our 
district nearly all have gone north to the Clyde Sea-area, 
supports this view, which was regarded by the late 
Hydrographer, Admiral Sir William Wharton, as being 
a priori probable (see ** Fishes and Fisheries of the Irish 
Sea, p. 9}: 
The following further account of the minor tidal 
currents in the immediate neighbourhood of the Isle of 
Man is given as the result of our own observations and 
information derived from Mr. James Crebbin, Captain of 
the yacht, and from the Port Erin fishermen (see Chart, 
fo), 
