Previous to the voyage, therefore, the ship’s burthen ought to be more carefully ascertained than, perhaps, raw inexperienced navigators have hitherto imagined.
The ship’s pumps.
6. The pumps ought to be formed on the most approved plan, and kept in perfect order. Some prefer Mr. Fulton’s patent pump, worked by a cylinder, and described in the Repertory of Arts, vol. III.
Mr. Clarke, Surgeon, at Sunderland, proposes an easier and more expeditious method of working the pumps, by means of a curved lever, which acts by an easy motion of the body, as in rowing. It has been found, on trial, to deliver twice the quantity of water, and with far less labour, than that with the brake—a circumstance of no small consequence, especially when seamen are almost worn out with sickness or fatigue[[6]].
[6]. See Repertory, Vol. IX.
Mr. Dearborn, an ingenious American mechanic, has accomplished a still farther improvement, by constructing a new machine to answer the double purpose of a pump and a fire-engine[[7]].
[7]. Ibid. Vol. III.
Mr. Taylor, of Southampton, we are credibly informed, has invented a ship pump, which, in point of simplicity and ingenuity, surpasses all others, and bids fair to supersede them in the British navy.
Ship’s compass.
7. The magnetic power of the mariner’s compass is liable to be disturbed by various accidents, as the rolling of the ship in a rough sea, the explosion of the great guns, and particularly lightning. Nay, even the electricity of the glass cover, when excited by the slightest accidental friction, is sufficient to alter its direction; but this can be soon remedied by wetting the glass, which carries off the electricity. In thunder storms at sea, the polarity of the needle has sometimes been suddenly reversed, and irreparably damaged, by the North and South points changing their station, occasioning, at the same time, dangerous errors. By this accident, a ship has been known to take a retrograde course, and steer above 100 leagues by a needle, the polarity of which had thus been totally changed[[8]].