the operation of trying the depth of the sea, and the nature of the bottom, by means of a plummet sunk from a ship to the bottom.

There are two plummets used for this purpose in navigation; one of which is called the hand-lead, weighing about 8 or 9 pounds; and the other the deep-sea lead, which weighs from 25 to 30 pounds; and both are shaped like the frustum of a cone or pyramid. The former is used in shallow waters, and the latter at a great distance from the shore; particularly on approaching the land after a sea-voyage. Accordingly the lines employed for this purpose are called the deep-sea lead-line, and the hand lead-line.

The hand lead-line, which is usually 20 fathoms in length, is marked at every two or three fathoms; so that the depth of the water may be ascertained either in the day or night. At the depth of two and three fathoms, there are marks of black leather; at 5 fathoms, 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 leamen, is generally performed by a man who stands in the main-chains to windward. Having the line quite ready to run out without interruption, 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 five fathoms is close to the surface of the water, he calls, 'By the mark five!' and as there is no mark at four, six, eight, &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 three quarters more than a particular number, he calls it a quarter less than the next; thus, at four fathoms and three fourths he calls 'A quarter less five!' and so on.

The deep sea lead is marked with two knots at 20 fathoms, three at 30, four 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 adhere 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.

A machine for the same purpose has been invented by Mr Massey, of which the following description is given:

"The importance of obtaining true soundings at sea must Sounding be admitted by every seaman; and it is rather singular, that no other method than the common lead has hitherto been brought into use; as its imperfections are very generally acknowledged.

"Many vessels have been lost, by depending upon the soundings taken in the usual way. The difficulty of obtaining the true perpendicular, and the uncertainty as to the exact moment when the lead strikes the bottom, upon which the accuracy of the result depends, must always prevent the possibility of obtaining the true depth, while the ship has any considerable way upon her. Indeed, it has been acknowledged by experienced seamen, during some experiments, made at various times, in the river Mersey, that they could not depend upon the common lead, when going five or six knots in the hour, in ten or twelve fathoms of water. When the depth is considerable, the vessel must be hove to, which is an operation attended with great loss of time, and sometimes considerable injury to the sails; and during a chase, this inconvenience must be particularly felt.

"True soundings may be taken with this machine in thirty fathoms water, without the trouble of heaving the vessel to, although she may be going at the rate of six miles in the hour. True soundings may also thus be obtained in very deep water, where it is not possible to take them by the common lead.

"Fig. 1. represents the sounding machine. \(a\) is the founding weight, containing a register, \(i\), \(2\), with two dials: the hand of the dial \(i\) makes one revolution when the weight has descended twenty fathoms, the other revolves once when the descent amounts to five hundred fathoms. A rotator, \(b\), similar to that attached to the log, communicates with the wheel work of the dials \(i\), \(2\), by means of the rod \(c\), on which there are three universal joints, \(3\), \(4\), and \(5\). This rod is supported during the descent of the weight, by the drop, \(d\), at the end of which is a fork, \(6\), and a friction wheel, \(7\).

"When the machine is to be used, a founding line is fastened to the ring, \(e\); and one of the vanes of the rotator is slipped into the spring \(8\); the rotator will then be in the position indicated by the dotted lines, \(x\). The indices must be set at \(o\), and the cover or lid, \(f\), be shut. The machine must then be projected perpendicularly into the sea. As soon as it reaches the surface, the resistance of the water forces the dotted rotator, \(x\), out of the spring \(8\), and it assumes its perpendicular direction as represented by the rotator \(b\). As the machine descends, it is evident the rotator will revolve, and its motion be communicated freely past the friction wheel \(7\), and the universal joint \(5\), to the wheel work of the dials \(i\), \(2\), and thus indicate the space passed through in fathoms. When the machine has arrived at the bottom, the rotator, as it is no longer buoyed up by the reaction of the water, will fall to the bottom, quitting the fork of the drop \(d\), which will also fall from its horizontal position, and in its descent, by means of the locking rod \(9\), prevent the rotator from revolving as the machine is drawn up. When at the bottom, the rotator will be in the position of the dotted lines \(y\).

"This machine, simple in its construction, and scarcely more liable to accident than the common lead, ascertains, with the utmost precision, the perpendicular depth, by the mere act of descent through the water. No mistake can arise from that common source of error, the drift or lee-way of the ship during the time of descent; nor does an operation of such importance depend upon Sounding, the uncertain sensation caused by the lead striking the bottom, on which the accuracy of the common log altogether depends, and which, it is well known, frequently and materially misleads the best seaman: for though a thousand fathoms of line were paid out, in the smallest depth of water, no inaccuracy could arise, as the perpendicular depth, at the point of heaving, would be registered on the index. The only inconvenience experienced would be the additional labour necessary for hauling in the excess of line. The most inexperienced person may use this machine, without risk of error, in the most turbulent sea, and during the night.

"The advantages already enumerated would render the founding machine of great importance; but there are other properties of still more consequence.

"To heave a ship to, in order to obtain soundings, on a lee shore, in stormy weather, is a very disagreeable operation, attended with much trouble, and loss of way; also with considerable danger to the ship's sails; indeed, it would often, under such circumstances, be attended with great hazard to the safety of the ship. To avoid these unpleasant consequences, the master sometimes adopts a measure, which he conceives to be the least exceptionable alternative, by running on without founding at all.

"To prove how much inconvenience and danger are avoided by Maffey's lead, it is enough to state, that soundings may be taken in depth from 60 to 80 fathoms, while the ship is under way, at the rate of three miles an hour; and as the rate of falling may be still materially reduced, without entirely stopping the vessel, or altering her course, so may soundings be had, to any depth required, while she is under way.

"In order more clearly to show the superiority of this machine, and make it apparent, that the quantity of stray-line veered out does not at all affect the truth of the result: suppose the common lead thrown from the mizen chains of the ship, which may be represented by the point \(a\) of the triangle \(abc\) (fig. 2.), and that the ship Fig. 2. has moved forwards through the space equal to the line \(bc\), while the lead has descended through the line \(ac\); it is evident, that it is impossible, in this case, to ascertain the exact depth, as a quantity of line, equal to \(ab\), would be paid out, whereas the true depth is equal only to the line \(ac\), which is much less. But the case is very different when the patent founding machine is used, as the operation ceases when it has reached the bottom; nor is the stray-line, \(ab\), whatever its length, at all taken into the account.

"It has been extremely difficult, and sometimes impossible, to obtain soundings in very deep water with the common lead, which may perhaps be thus accounted for. The common line which is used for founding, though, if left to itself, it would sink in water, yet its descent would be much slower than that of the lead, separately; it consequently follows, that the lead must be so much impeded by carrying the line with it, that when it does reach the bottom, there will be scarcely any sensible check to enable the seaman to know the precise moment. Indeed, if he can ascertain even this to a certainty, he still cannot depend upon the truth of his soundings; for if there be the least drift or current, the line itself will assume a curve, similar to that of the line of a kite in the air. These two causes will always operate..." After so fully describing the principle of the patent founding machine, it is scarcely necessary to prove, that it is liable to neither of the foregoing objections; and it may be sufficient to say, that, as it will certainly find its way to the bottom, if a sufficient portion of iron-line be allowed to guard against its being checked in its progress, and the certainty of its having reached the bottom may be ascertained by the arming, there can be no doubt of the practicability of its obtaining foundings, in any depth, and no reasonable doubt of their correctness when obtained.

From the construction of this machine, it might be imagined, that the rotator would impede its motion through the water, and that it could not descend so rapidly as the common lead; but during repeated trials, in thirteen fathoms water, in which the rotator was frequently detached, and the lead suffered to descend alone, there was no difference perceptible in the time of their descent, though an excellent quarter second stop watch was used during the experiment, to detect any change. The following table shows how very uniformly the times of descent corresponded with the depths in fathoms, during a series of trials made on the river Mersey, with the patent lead, weighing 14 pounds.

The manner of conducting these experiments was such as is deserving of perfect reliance. Two pilots, of well-known ability and experience, were employed: one threw the lead, and the other, the moment he found, by the slackening of the rope, that the weight had arrived at the bottom, cried 'stop,' to a third person who held the watch.

| Time of descent | Fathoms | |----------------|---------| | 2 seconds | 2 1/2 | | 2 1/2 | 3 | | 3 | 4 | | 5 | 8 | | 5 1/2 | 8 1/2 | | 6 | 10 | | 6 | 10 | | 7 | 11 1/2 |

Taken when under sail, at upwards of five knots in the hour.

Several captains and masters in the navy have made trial of the log and founding machine, and given very favourable reports of their performance; and it has been adopted by order of the Navy Board in the British navy.*