The laxity of the present methods having been brought, by his friend Captain Cockburn, R.N., before the author, with a desire to be furnished with some sort of anemometer, and with some easy means of eliminating the effect of the motion of the vessel, he began to consider what would be the most appropriate form of anemometer to be used at sea; for several kinds had been already tried, but had failed, as he thought, from not being constructed on a suitable principle. The species which the author considered the best, was that which should imitate, as nearly as possible, mutatis mutandis, the log-line by means of which the ship's way through the water is determined; for that instrument seems to have preserved its situation and supremacy over all others on board-ship amongst all nations, and from the time of Columbus to the present, mainly on account of the appropriateness of the principle involved.