in an east by north direction—that is, towards D. It has already been shown that even a deep-keel boat, when close-hauled, is driven away to leeward, so that her real direction through the water is at an angle with the direction in which she is heading; and that a vessel will make greater leeway if the sea be rough. It is easy to measure the amount of leeway by looking over the stern and observing the vessel's wake—that is, the track she leaves behind her in the water; the angle the wake makes with the keel being the angle of leeway. We will suppose that this angle, in the present case, is about one point of the compass. Then our course through the water has been one point to leeward of east by north—that is, it has been east (magnetic), in the direction C E, which we now lay down with our parallel rulers on the chart. Next we calculate (having hove the log occasionally, or having made a rough estimate by looking over the side) how many miles we have travelled through the water since we left the point C, and with the dividers we measure out this distance from the scale of miles on the chart, and lay it down from C on the line of our course, making C E equal to the distance. E would then be our present position, had no current been running since our start.
But when we left C the flood-tide was just beginning to make, and has been setting us in a northerly direction for four hours. On reference to the arrow on the chart, we find that at half-flood the rate of
