The hand lead-line, which is usually 20 fathoms in length, is marked at every 2 or 3 fathoms; so that the depth of the water may be ascertained either in the day or night. At the depth of 2 and 3 fathoms, there are marks of black leather; at 5 fathom, there is a white rag; at 7, a red rag; at 10, black leather; at 13, black leather; at 15, a white rag; and at 17, a red ditto.
Sounding with the hand-lead, which is called heaving the lead by seamen, is generally performed by a man who stands in the main-chains to windward. Having the line all ready to run out, without interrupton, he holds it nearly at the distance of a fathom from the plummet, and having swung the latter backwards and forwards three or four times, in order to acquire the greater velocity, he swings it round his head, and thence, as far forward as is necessary; so that, by the lead’s sinking whilst the ship advances, the line may be almost perpendicular when it reaches the bottom. The person sounding then proclaims the depth of the water in a kind of song resembling the cries of hawkers in a city. Thus, if the mark of 5 fathoms is close to the surface of the water, he calls ‘By the mark five!’ and as there is no mark at 4, 6, 8, &c. he estimates those numbers, and calls, ‘By the dip four,’ &c. If he judges it to be a quarter, or an half more than any particular number, he calls, ‘And a quarter five! and a half four,’ &c. If he conceives the depth to be 3 quarters more than a particular number, he calls it a quarter less than the next: thus, at 4 fathom and ¾, he calls ‘A quarter less five!’ and so on.
The deep-sea-lead is marked with two knots at 20 fathom, 3 at 30, 4 at 40, and so on to the end. It is also marked with a single knot in the middle of each interval, as at 25, 35, 45 fathoms, &c. To use this lead more effectually at sea, or in deep water on the sea-coast, it is usual previously to bring-to the ship, in order to retard her course: the lead is then thrown as far as possible from the ship on the line of her drift, so that, as it sinks, the ship drives more perpendicularly over it. The pilot feeling the lead strike the bottom, readily discovers the depth of the water by the mark on the line nearest its surface. The bottom of the lead being also well rubbed over with tallow, retains the distinguishing marks of the bottom, as shells, ooze, gravel, &c. which naturally adheres to it.
The depth of the water, and the nature of the ground, which is called the soundings, are carefully marked in the log-book, as well to determine the distance of the place from the shore, as to correct the observations of former pilots. See Coasting and Navigation.
SPAN, pendour (spanna, Ital.) a small line or cord, the middle of which is usually attached to a stay, from whence the two ends branch outwards to the right and left, and having either a block or thimble attached to their extremities. The intention of the span is accordingly to confine some rope which passes through the corresponding block or thimble, as well to increase the effort of the said rope, as to prevent it from swinging at too great a distance from the centre of its action in stormy weather. Such are the spans occasionally used for the top-gallant braces, or the fore-top-gallant bowlines, &c.
Span-shackle. See the article Davit.
SPARE, rechange, an epithet applied to any part of a ship’s equipage, or furniture, that lies in reserve, to supply the place of such as may be lost, or rendered incapable of service. Hence we say, spare top-masts, spare sails, spare rigging, &c.
PUMP-SPEAR. See the article Pump.
SPELL, the period wherein a sailor, or gang of sailors, is employed in a particular exercise, from which they are relieved as soon as the limited time expires. Such are the spells, to the hand-lead in sounding; to the pump; to look out on the mast-head, &c. and to steer the ship; which last, however, is generally called the trick. See Steering.
Spell also implies the relief, or the return of duty to those services: Thus we say, spell the pump, spell the lead, &c.