DEEP SEA LEAD LINE.

Weight of Lead 28 to 30 lbs.

Is marked the same as a hand line up to 20 fathoms, then with one knot at 25 fathoms, three knots at 30, one knot at 35, four knots at 40, and so on to 95.

Then at 100 fathoms a piece of bunting, at 105 one knot, at 110 a piece of leather, at 115 one knot, at 120 two knots, and so on as in the first 100 fathoms.

Massey's Sounding Machine.

The register wheels are set at the starting points, the small one at the 10 fathom mark; and the large one on the opposite side at the 150 fathom mark, the catch is then shut down on the fan. On entering the water the catch is lifted and the fan revolves until bottom is reached, when the fan stops and the catch falls on it. It registers the depth in fathoms.

Walker's Harpoon Sounding Machine.

THE first wheel marks one revolution in 30 fathoms; and the second, one in 150 fathoms.

The dials are set by turning the button on the first dial until the pointer is opposite the number 30, and the index of the wheel on the other side of the machine points to 150.

Burt's Nipper and Buoy.

Is a small metal apparatus, similar to a snatch block, attached to a canvas conical bag which acts as a buoy; the line is snatched in the block, the whole forming a sort of floating pulley. As long as the strain of the descending lead is on, the lead line runs freely, at the same time the bag is, to a certain extent, submerged. On the strain being removed, by the lead reaching the bottom, the line is nipped by a spring, and the bag rising to the surface gives notice that the sounding has been obtained, and that the line may be run in.

Log Line

Is marked with a piece of bunting at the end of the stray line.

One knot at every half-knot.

A piece of leather at the first knot.

Two knots at two knots.

Three knots at three knots, and so on.

The log line is measured to correspond with a glass running 28 seconds. When the 14 second glass is used, the distance on the log-line must be doubled.

To calculate the length of a knot on the log line.

3600s 28: 6080-ft. required length=47-ft. 3in.

:

The log line should be repeatedly examined, by comparing each knot with the distance between the nails, which are (or should be) placed on the quarter-deck for this purpose, at the proper distance. The line should be wet whenever it is required to re-measure it, or to verify the marks.

When heaving the log, the log ship should be thrown out well to leeward to clear the eddies near the wake, and in such a manner that it may enter the water perpendicularly, and not fall flat upon it before a heavy sea the line should be paid out rapidly when the stern is rising, but when the stern is falling, as this motion slacks the line, the reel should be retarded.

The sand-glasses should frequently be tested by a good watch, as in damp weather the sand does not run freely, and sometimes hangs in the neck of the glass.

Massey's Patent Log is a piece of mechanism which being towed from the quarter, with line enough to clear the eddy in the wake of the ship, shows the distance actually gone through the water by means of the revolutions of a fly, which are registered upon a dial plate to knots and tenths. Patent logs should be tested when ships are running the measured mile.

Walker's Harpoon Ship Log is on the same principle, but the rotator is a continuation of the part that holds the wheelwork. The dials are the same as in Massey's.

M

Table for converting French Metres and Décimetres into English Feet and Fathoms.

By Robert C. Carrington, F.R.G.S., Hydrographic Office, Admiralty.

Table for converting French Metres and Décimetres into English Feet and Fathoms.-(continued.)

SPHEROIDAL TABLES.

SHOWING the length in feet of a degree, minute, and second, of latitude and longitude, with the corresponding number of statute miles in each degree of latitude, and the number of Minutes of latitude, or Nautical miles, contained in a degree of longitude, under each parallel of latitude.--For every degree.

*The figures in this column, divided by 6, will give the length, in cables, of a minute of longitude in its corresponding latitude, thus: in latitude 51°=37861÷÷÷6 =631 cables in a minute of longitude.