858 
BULLETIN OF THE BUBEAU OF FISHERIES 
Readings of the current meter (or the simpler method of employing a float) 
give the rate of the current over a known interval of time and its direction . 52 These, 
then, are reduced to average velocities and directions for each tidal hour after the 
time of high water at some neighboring station of reference, and it is in this form 
that they appear in the current tables published in the United States Coast Pilot 
(United States Coast and Geodetic Survey, 1911, p. 151) and in the current tables 
for the Bay of Fundy (Dawson, 1908). In all such tables the direction stated is 
that toward which the current flows, referred to the true meridian. In other words, 
a “northeast” current is just the opposite of a “northeast” wind. 
To plot the course which an imaginary body, floating in the water, would travel 
during the period from one high tide to the next, is perhaps the most graphic way 
to bring out the existence or absence of a dominant drift at any given locality. If 
the flood and ebb currents are exactly opposite in rate, duration, and direction, 
such a float would return precisely to its starting point, for there would be no 
resultant drift. In all probability, however, this would never happen in any part of 
the Gulf of Maine. If, with ebb and flood opposite in direction throughout their 
respective duration, one were stronger than the other, a dominant set would result 
parallel to the direction of the stronger. This condition is to be expected in nar- 
row channels, such as the Grand Manan Channel, and close in along some parts of 
the coast line; but in most parts of the gulf the direction of the tidal current 
changes from hour to hour, running in a comparatively constant direction for only a 
few hours when ebb or flood is at its strength. In some localities the tidal current 
is perfectly rotary, with its direction veering uniformly throughout the half-tidal day. 
Such a state, for example, is to be expected about 16 miles to the eastward of Nan- 
tucket Shoals light vessel (United States Coast and Geodetic Survey, 1912, p. 10). 
In the Gulf of Maine and on its offshore banks tidal currents veer always to 
the right — i. e., with the hands of the clock — most rapidly, in most cases, at the 
times of high and low water. Thus, a particle of water or any floating object, such 
as a buoyant fish egg, drifting during a tidal period, would follow a course varying 
in different parts of the gulf from a closed circle (bringing it back close to its 
starting point), through various types of veering spirals, to courses nearly opposite 
in direction for the two tides but unequal in distance. In most parts of the gulf, 
therefore, any such floating object would not follow the dominant or nontidal set 
directly, but in a zigzag or spiral course, traveling a much greater distance in the 
daily tidal components than the distance made good along the azimuth of the non- 
tidal set. 
The dominant set that results from a veering current may be deduced in various 
ways. If calculation be preferred, an approximation is easy with the ordinary navi- 
gational traverse tables in precisely the same way the navigator calculates, from 
his dead reckoning, the distance and course made good for the day. 
In most cases a graphic method of summation is to be preferred. The following 
(now in common use and recently described in detail by Mavor (1922)) is, perhaps, 
“ It should be borne in mind that in tabular statements of currents the words “velocity ” and “distance” are not synony- 
mous; for, obviously, if the current is flowing at a rate of 1 mile per hour at one hour, and at 2 miles per hour an hour later, the 
distance made good during the interval is neither 1 mile nor 2 miles, but the mean of the two. This caution is added because 
some of the published tables of currents have been ambiguous in this respect. 
