N, making L N parallel to the direction of the current. Then we take the number of miles which we estimate the vessel will sail in one hour, and with this distance as a radius and N as a centre describe a circle. We join M, the point where this circle cuts the line L P, with N; and from L we draw L O equal and parallel to N M. L O is the direction in which we must steer to keep the vessel on the line L P, and also represents the distance that must be sailed in order to reach M.
In the above example, the current affects the ship's course as well as her rate of progress over the ground. If the current's drift is in the same direction as the ship's apparent course there is no alteration of her course, but the distance travelled will be the sum of the distance logged and the number of miles of the current's drift; and if the two are in opposite directions, it will be the difference between these. Thus, had we sailed from C on the starboard tack, we should have travelled over the ground in the direction we were heading—that is, north; and C Y, the distance we should have made, would have been equal to C E plus E F.
I have taken it for granted, in this description of our proceedings, that the flood-tide preserves a uniform northerly set. This, by the way, is unlikely to be the case. In the open sea the tide, as a rule, runs in different directions at different hours of the flood—for example, setting north at half-flood and north-east at the fourth hour,—and this difference
