1. An expert American seaman recommends to mariners the experiment of hanging out a line of cable over the stern of a small vessel, or boat, in a rough sea, as this appendage serves to make a long wake, and will be found to enable the vessel (according to the sea term) to live much longer in a heavy gale. Little danger, he observes, is to be apprehended from a long sweeping swell of the sea; the mischief generally arises from overhanging surges, which at once break in and overwhelm the vessel. Having often experienced, in stormy weather, the beneficial effects of a long coil of rope fixed to a flat piece of wood, and appended to vessels, he thence endeavours to explain the extraordinary efficacy of the tow-line in balancing the ship, and lowering the high-swelling surge.
2. From the Transactions of the Philosophical Society, at Philadelphia, we learn, that Mr. Hopkinson has invented an instrument, with a graduated tube, which, from the difference of specific gravity between oil and water, by its rise and fall, accurately measures the ship’s progress. Also, a curious spring block, by which sailing is greatly expedited; for which useful invention he obtained the Society’s gold medal.
3. Mr. Gearson, of York-town, Pennsilvania, has lately obtained a patent for an important invention, by means of which, we are informed, that a vessel whose bottom is so shattered, that the ordinary pumps could not, for one hour, prevent her sinking, will be effectually kept buoyant; and, though under a press of sail, be incapable of being overset by the heaviest gale.
4. A gentleman of Rotterdam has invented a new floating machine, which, though small, is capable of holding four men commodiously, and may be enlarged sufficiently to accommodate fifty, if required. So curious is its construction, we are told, as to enable it to withstand the utmost fury of the winds and seas. It can neither overset, nor sink, and may therefore, in the most stormy weather, be steered whatever course the pilot shall see necessary. These last may be considered as different modifications of the life-boat, constructed with the same humane views, though probably without any communication between the respective artists. Were packet-boats destined to convey important dispatches thus constructed, many unfortunate accidents might be prevented.
The comparative value of these and other laudable inventions, whether produced by foreigners, or our own countrymen, must rest with their ingenious authors, at least, till their respective merits be fully ascertained by actual experiment. Were models of every new and useful contrivance, of this nature, consigned to the board of Naval Architecture, for public inspection, the display of such an assemblage of mechanism would excite emulation, and the result of satisfactory trials, if communicated from time to time, might prove highly important to the maritime world.
5. It is certain, that a ship will carry a weight equal to that of a quantity of water, of the same bulk with itself, deducting, however, the weight of metal employed in its construction; for the wood is nearly of the same weight with water. Were it not for the iron, or other metal, a ship might float though full of water. However it be loaded, therefore, it will not entirely sink as long as the weight of its cargo is less than that of an equal bulk of water.
Now, to ascertain this, the capacity of the ship must be measured. Suppose it to be 1000 cubical feet, multiply that by 73 pounds, the average weight of a cubical foot of sea-water (taken at a proper distance from shore), which gives in the product 73,000 pounds for the weight of a bulk of water equal to that of the ship, the burthen of the ship being 73,000 pounds, or 36 ton and a half, reckoning a ton 2000 pounds, that being the weight of a ton of sea-water. If the cargo exceeds 36 ton and half, the ship will sink; if just 73,000 pounds, she will swim, though very deep in the water, and on the very point of sinking. And though she may float at sea, she will sink on entering the mouth of a river; fresh water being specifically lighter than sea-water, and in the proportion of about 63 to 73.
Previous to the voyage, therefore, the ship’s burthen ought to be more carefully ascertained than, perhaps, raw inexperienced navigators have hitherto imagined.
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.
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].
8. Phil. Trans. Abridged, by Lowthorp, vol. II. p. 180.
The compass, though long known, was imperfect and liable to many inconveniencies, till at length, by the ingenuity of Dr. Knight, it was greatly improved; and has since undergone a further emendation by Mr. Smeaton. The improvement consists in the shape and temper of the needle; in the discovery of proper means for restoring the loss of magnetism in a voyage; and, finally, in rendering it less subject to be influenced by the motions of the ship. These contrivances, though found too delicate always to sustain with impunity the rude shocks of a tempestuous sea, or the more violent stroke of lightning, are, however, the best that have been yet discovered. Therefore, as this improved compass is allowed to be superior to others, and is now generally used in the royal navy, it ought certainly to be provided for all merchant ships, particularly on long voyages.
8. The power of the rudder being reducible to that of the lever, and oblique action of the water, the most advantageous angle made by the helm from the keel, mathematicians have fixed at 54° 44′. Euler recommends an obliquity somewhat less; and establishes this rule, that an obliquity of 48° will, in general, produce the most powerful effect; though experience testifies, that a ship steers tolerably well when the rudder makes an angle of only 35°.
A convenient substitute for the loss of a rudder has been invented by captain Pakenham, for which useful device the Society of Arts presented him with a gold medal. The method, being described at large in the Society’s Transactions, need not be repeated in this place.
9. To the mechanical genius of captain Pakenham, the navy is also indebted for an easy, cheap, and expeditious, method of restoring a mast, when injured, or decayed, by simply inverting the mast and turning the heel to the head; of which the Society, in the 10th volume of their Transactions, have given a full description, illustrated with an engraving.
The sudden damage which masts frequently sustain from sea-storms and naval engagements, and which, in the ordinary way, require from six to eight weeks to refit, may thus, we are assured, be repaired within forty-eight hours; and that this method is equally applicable to all ships, from a first-rate, to the smallest merchantman—a matter of no small consequence on long voyages, or in time of war.
10. A ship, properly equipped for a long voyage, ought to be provided with a complete set of nautical instruments, including an accurate thermometer, barometer, and time-piece. Also, a life-boat, cork jackets, cords, drags, buoys, and other implements for the prevention of drowning.
From the result of three successive voyages from Europe to America, captain Williams, under the direction of Dr. Franklin, found the temperature of the main ocean, out of soundings, at least ten degrees warmer than in shallower water near the coast. Hence the thermometer may serve a new and important purpose in pointing out the near approach to shore; also, in detecting latent rocks, or banks of sand or coral, concealed under water. Is the decrease of temperature owing to these solid bodies acting as conductors, and thus conveying off the heat?
A curious and unsuspected cause of inaccuracy in watches, or time-pieces, has lately been discovered by an ingenious artist, which well deserves notice. The balance, being made of steel, is very liable to acquire a polarity, which disturbs the regularity of its movement, according as the watch happens to be placed North and South, or in the vicinity of a knife, a key, or other steel utensil. On trying a variety of steel balances, by floating them on cork, placed on the surface of water, Mr. Varley could scarcely select one that did not betray some sign of polarity; nor can this be easily prevented, but by substituting a balance of gold, or some other metal. May not this be one reason why that grand desideratum, a perfectly correct time-piece for discovering the longitude at sea, has not yet been produced?
To prevent accidents during long voyages, the Transactions of the Royal Society of London suggest many important hints; which, however, for the sake of brevity, must be omitted, by referring the reader to the respective passages, viz.
1. To preserve vessels from the worm, by a more cheap and durable method than that of sheathing; also, to prevent leakage from the same cause.—See Phil. Trans. vol. VIII. p. 6192.—Vol. XLIII. p. 370.
2. To preserve the health and lives of men crowded in slave ships, and transports, by ventilators, and other means.—Vols. XLIV, and XLVII. p. 211.
3. To measure the ship’s way more correctly than by the log, &c.—Vols. XXXIII, and XXXVIII.
Also, a still later method, with improvements. See Memoirs of the American Philosophical Society, vol. II.