CHAPTER XIV.

ANCHORING AND RIDING OUT GALES IN DEEP WATER.

A general rule for anchoring is to give a scope of chain three times the depth of the water, but a safer rule is to give five or even six times the depth.

In anchoring, it is desirable to lay the chain out straight, clear of the anchor. This can be accomplished by keeping headway, or by giving the vessel sternboard before letting go.

If anchoring in deep water it is best to lower the anchor into the water until its weight is taken by the chain, and then let go from the stopper inboard. In cases of anchoring in very deep water it is well to ease the anchor down to within ten or twenty fathoms of the bottom before letting go; by doing this, command can be retained over the chain, and there is less danger of losing it.

A long scope of chain acts as a buffer against the strain of sudden jerks on the anchor and chain, caused by the ship veering about, and rising or falling to the waves. The longer the scope the greater the resistance to this disturbing power.

To increase the value of the long scope a heavy kedge, or other weight, may be secured to the bight of the cable; then veer out more chain; this will bring the strain more in a horizontal direction at the anchor and prevent the latter from tripping.

North Sea fishermen, in their small vessels, use a large cask on their cables during gales of wind, secured between the vessel and the anchor, in order to reduce the direct strain on the ground tackle.

It is recommended to use an empty cask for this purpose, in case of need, and if arrangements are made for running out oil bags to the same before it is launched, the force of the sea will be much reduced, as shown in the article on the subject of oil.

This barrel buoy serves two purposes; the vessel in veering about rides more directly from the barrel buoy than from the anchor itself; hence there is less disturbing force brought upon the anchor, and less probability of fouling it.

By taking up the strain of the chain as the vessel rides up, it guards against the quick-snapping action on the chain when the vessel tautens it

out again, the buoy being dragged through the water counteracting in part this strain.

During the war of the rebellion it was a common practice for vessels on blockading duty to ride out heavy gales of wind at sea, and on a lee shore, while at anchor, with a long scope of chain, and without using oil. Admiral Porter's reports of the operations against Fort Fisher, on the coast of North Carolina, mention numerous instances of severe gales being encountered while at anchor at that point without any accident.

EXTRACTS

from the log books of several vessels during the gale of December 20 and 21, 1864, off Beaufort, North Carolina.

U. S. S. Brooklyn: On December 15, anchored with starboard anchor in 15 fathoms of water, veered to 45 fathoms of chain. On December 20 and 21 the wind freshened gradually to a fresh gale from the SW. and a heavy sea made. Early on the morning of the 21st, veered to 75 fathoms and at noon to 100 fathoms. Started engines ahead slow to ease chain. Heavy sea. Ship rolling heavily. Force of wind 7-9. On the 23d, the gale abating, hove in to 50 fathoms.

U.S. S. Colorado: Anchored on December 15, in 16 fathoms of water, veered to 60 fathoms of chain on starboard anchor. December 21, fresh gale, veered to 135 fathoms and started engines ahead slow. December 23, hove up starboard anchor and found the arms broken; let go port anchor.

U. S. S. Tuscorora: Anchored December 19, in 10 fathoms, veered to 55 fathoms on starboard chain. December 21, ship dragging, veered to 90 fathoms and steamed ahead slow. December 22, got underway, anchoring

later in 11 fathoms with 90 fathoms of chain.

U.S. S. Juniata: Anchored in 13 fathoms of water with 45 fathoms of chain on starboard anchor, on December 19. On the 20th, a fresh gale blowing, with heavy sea running, veered to 60 fathoms. On the 21st, started to veer more chain. In veering parted stoppers, compressor bolt broke, and not being able to stop the chain, it tore the bolt out of the keelson and parted the end lashing, thereby losing 150 fathoms of chain and an anchor weighing 2,450 pounds. Got under way and stood out. Saw that nearly all the vessels in the fleet had dragged or were dragging their anchors. Twenty-second, anchored at 10 A. M. in 14 fathoms of water with 75 fathoms of chain on port anchor.

These vessels, were out of sight of land and on a lee shore.

CHAPTER XV.

CURRENTS.

" by

Extract from the "Currents of the Great Lakes, as deduced from the movements of Bottle l'apers during the seasons of 1892 and 1893," Mark W. Harrington, Chief of the Weather Bureau.

The currents in the Great Lakes are grouped under three heads:

1. The main currents:

A general set of the water toward the outlet exists in each of the Great Lakes, forming a continuous current in that direction.

The outlet of Lake Superior being on the southern side, this current hugs the southern shore. In Lake Michigan it hugs the eastern shore, the readiest access to the outlet being on that side, owing to the position of the islands at its northern end. The same rule holds good in Lake Huron as regards the western shore. In lakes Erie and' Ontario this phenomenon is not so plainly marked.

2. Surface currents:

These are due to the prevailing winds which have always been recognized as influencing the motion of currents in large bodies of water.

3. Return currents:

The outlets of the lakes being small and insufficient for the escape of all the water banked up by the wind, return currents are inevitable.

The theory has often been propounded that many ocean currents arise from the above cause; the water driven before the wind making the current, and the piled-up water seeking an escape, forming the return

current.

OTHER FEATURES.

Barometric changes, as well as other meteorological phenomena, may have an influence on the currents of the Great Lakes. A high pressure of the barometer lying over the southern end of Lake Michigan, for instance, will lower the water at that point, causing a difference of surface level between the two ends of the lake and a resulting flow of water to the southward. Such conditions, however, could hardly endure for any great length of time.

There also occurs occasionally on the Great Lakes a phenomenon which is called 66 a Seiche." It is a wave of considerable height, unaccompanied by other waves, appearing as a wall and moving rapidly.

From the above remarks it will be seen that the steadiness and persistence of the lake currents have not yet been determined accurately. Their velocities have been found to vary in speed from 4 to 12 miles a day.

The prevalence of westerly and southwesterly winds favor the strength and persistence of these currents, and it must be remembered that when the motion of the surface water has been communicated to the strata below, a brief change of wind, while affecting the surface, is not so soon communicated to the underlying water.

CURRENTS IN LAKE MICHIGAN.

A fresh wind of several days duration is well known to be of importance to the generally shallow harbors of the lake. Such a wind has a well recognized effect on the depth of water in the Chicago River.

As a result of experiments it has been found that a main current exists in Lake Michigan setting down the west coast about 10 miles off shore, sweeping around the south end, and stretching to the northward close to the east coast. Hugging the east shore, the current sweeps through the narrow passage east of the Manitou Islands, and thence by the Straits of Mackinac into Lake Huron, forming a whirl around the Beaver Island group on its way to this outlet.

This current is more clearly and strongly marked on the east shore than elsewhere, and it is to this that the freedom from extensive shoals and bars off the east coast is due, while broad shallows line the west coast.

Between the margin of the current and the west shore there are varying currents, sometimes to the northward and sometimes to the southward. There is a whirl around Beaver Island in a direction contrary to the hands of a watch.

The average speed of the current was found to be 4 to 43 miles per day. Through Manitou Passage the velocity was from 6 to 10 miles per day. Private observations, taken with great care, showed a current of from 36 to 96 miles per day (1 to 4 miles per hour) to the northward, off Manistee, Michigan.

Some confirmation of these conclusions can be obtained from the disposition of sand spits, shoals, bars, etc., the piling up of sand against the breakwaters, and the directions of the rivers after entering the lake, the eastern ones trending to the northward, and western ones southward.

In Green and Traverse bays the currents run up the different arms, but very little is known about them.