A chart is a representation of a portion of the surface of the earth intended to be useful to a seaman, and it therefore deals in detail with the portions of the earth covered with water. It gives the positions of lights and buoys, details of the sea bottom, and heights, magnetic variations, and soundings.
We drew a line on the chart from the positions, ten miles south of the North Hinder, where Perham had come down, towards the Dutch coast. This represented the direction the boat would drift owing to the wind.
The flying-boat, with two sea-anchors out, checking the drift, and also with weigh knocked off owing to the tossing of the waves, would probably not drift faster than three knots. Therefore the wind line was dotted off at three mile intervals.
Beside the movement due to the wind the flying-boat would move with the tide, so the set due to the tide was dotted on the chart at right angles to each three-mile mark.
When these dots were joined a wavy line was the result, a line first setting away from the main line of drift, then coming back to it, crossing it, and then setting away in the other direction. When the line got near the Dutch coast it could not be calculated owing to the curious currents, rips and eddies, set up by the low-lying nature of the land.
It was seen at once that the three boats would not be required next day. For Perham would drift past the Schouen Bank light-buoy about two o'clock in the morning and would be off the Dutch coast at Schouen by daybreak.
If the boat lived.
An extra heavy gust shook the building, and a great fall of soot down the chimney almost beat out the fire.
There was a general feeling of thankfulness and relief when the Duty Steward entered and asked if any one wished to give an order before the bar closed.