[pAwsoN] METHODS OF INVESTIGATION OF TIDES & CURRENTS 7 
theories were also disposed of, such as a constant inward flow through 
Belle Isle strait, which has undoubtedly led to the occurrence of 
wrecks. 
Pacific Coast.—In dealing with the passes and narrows in British 
Columbia a different procedure is necessary. The strength of the 
current is from 8 to 10 knots per hour, and it is impracticable to anchor 
a vessel for their investigation. Navigation through these passes is 
only possible at slack water, and vessels have to time their trips ac- 
cordingly. Several of the most important industries of the province 
are dependent upon towing, as in the transportation of lumber and 
coal; and a knowledge of the time of slack water is therefore essential, 
as the most powerful tugs cannot handle a coal barge, a raft, or a scow- 
load of freight cars when the current is running. 
In these circumstances, the method adopted is to observe the turn 
of the current from the shore. This has been done for several of the 
passes where there is any habitation or lighthouse from which ob- 
servations can be made. Other passes, through which an immense 
traffic goes, have uninhabited shores. A consequent difficulty is to 
obtain correct time. It is necessary to place a meridian instrument 
by which the time can be obtained direct from the sun, or to furnish 
the observer with a chronometer. 
The object in view is to ascertain the time of slack water relatively 
to the time of the tide as observed simultaneously at some principal 
station. A basis is thus obtained for the calculation of a slack water 
table in advance, similar to a tide table. In reducing the observations 
for this purpose, it was found that the time at which the current turns 
is not constant with relation to the time of high and low water; but 
in the difference between the two, there is a variation of a complex 
character, because of the half tides and other special features in the 
tidal fluctuation. The annual variation is so large that it is essential 
to continue the observations throughout the course of the year, to ob- 
tain a satisfactory basis for calculation. 
When these variations are determined, the time of slack water 
can be computed in advance from the calculated tide tables. In this 
way, slack water tables are now published annually for First Narrows 
at the entrance to Vancouver harbour, Active Pass and Porlier Pass; 
and good determinations have been obtained also for Seymour Narrows. 
Atlantic Coast.—When a vessel and funds were again available 
for current investigation, the seasons of 1903 and 1906 were given to 
the steamship routes around the south coast of Newfoundland and to 
a more systematic investigation of Belle Isle strait. The question of 
indraught into the large bays on the south coast of Newfoundland 
was fully examined, because many wrecks were attributed to this 
