Hi bugman1912,
Thank you for the interesting question! Simply put, the cable was
loaded onto ships and rolled out, different grades of cable were used
for the various depths and the ends spliced as they went. Splicing new
cable and repairing cable were accomplished by grabbing the end of the
cable with a grapnel and bringing it into the ship for splicing. I've
copied and pasted small sections of historical articles, but click on
the links for some great descriptions and photos.
>>>>>> History of the Atlantic Cable & Submarine Telegraphy
From the first submarine cable of 1850 to the worldwide fiber optic network:
http://www.atlantic-cable.com/
How would they handle deep trenches?
1) Sounding
Laying a Deep-Sea Cable Line - 1923:
"The laying of long submarine cables is not an easy matter. It is a
well-known fact that the contour of the ocean's bottom varies
similarly to that of dry land. It has its rolling and steep hills, its
valleys and plateaus. It therefore is necessary to know the contour of
the ocean bed before the cable is laid. This is essential to avoid
suspending the cable between two hills, where it would hang in a
festoon, or like a clothesline between two poles. Such suspension soon
would cause the cable to wear because of its own weight."
"The route over which the cable will lie must be more carefully
surveyed than the course for a new railroad over prairies, through
forests and across mountain passes. The ocean survey consists of a
series of deep-sea soundings which not only furnish the depth of the
water and samples of the water, but also produce specimens of the
ocean bottom and the temperature of the water, all of which are
important factors in the laying of submarine cables. If by chemical
analysis it should transpire that there is any mineral deposit on the
bottom of the ocean which would injuriously affect the cable, or if
the temperature should show that there was volcanic action at certain
places, these must be avoided. Deep-sea sounding machines have been
invented to obtain this information. Samples of the sea water along
the ocean bed and also the earth deposits are brought to the surface
for examination. A specially constructed thermometer that will
withstand the terrific pressure at great depths is used in this
connection."
http://www.atlantic-cable.com/Article/1923CableLaying/index.htm
How did they place the wires?
2) Laying
From McClure's Magazine, Vol. VIII No. 3, January 1896:
"The Making and Laying of an Atlantic Cable" by Henry Muir:
"In laying a cable it is of the first importance to have the cable
always under control. Control is secured first by passing the cable
under and over a series of grooved iron wheels, running aft down the
centre of the ship's deck. The hold thus obtained is considerable, but
it is the greater if the cable comes slightly bent from the tank. From
the series of wheels the cable runs over a pulley, and passes three
times around a drum some eight feet in diameter. Connected with this
drum is a brake which is used to restrain the cable from paying out
too fast. A cable pays out too fast when it goes to the bottom slack
instead of taut; and, in spite of the fact that the ship is always
steaming ahead, and the further fact that the water in its resistance
supplies something of a check, yet as the cable weighs some two and a
half tons to the mile, its own weight would pull it over much too
rapidly, were it not stopped by the brake."
http://www.atlantic-cable.com/Article/mcclures/1896mcclures.htm
How did they fix the wires?
3) Repair
1915: How submarine cables are made, laid, operated and repaired:
"Supposing, therefore, that the known resistance per mile is two ohms,
and the measuring apparatus indicates a total resistance in the broken
cable of 800 ohms. The break would thus be ascertained by dividing the
800 ohms by 2, which would place it 400 miles from the shore. With
this information the captain of the cable-repairing steamer is able to
determine, by his charts showing the position of the cable, the
latitude and longitude in which the break has occurred, and the ship
proceeds to the repair. Having arrived at a point near which the cable
is broken, a mooring with buoy attached is put overboard to mark the
position."
"...The ship then steams to a convenient distance from the broken end
of the cable; a heavy iron grapnel is lowered and is dragged along the
bottom of the ocean at right angles to the line of the cable for the
purpose of hooking it. There are different kinds of grapnels, but all
have the same general features. The ordinary kind has a shank about 4
feet long with five prongs and weighs about 230 pounds. This style of
grapnel is used for general work. For very deep water work a special
type of grapnel is used, which cuts one side of the cable and clutches
and holds the other. This is done to avoid excessive strain on the
cable when lifting the cable from great depths."
http://www.atlantic-cable.com/Article/1915CCC/index.htm
Repairs - Making the Splice:
http://www.atlantic-cable.com/repairs/repairs.htm
Very enjoyable research. If you have any questions, please post a
clarification request before closing/rating my answer and I'll be
happy to reply.
Thank you,
hummer
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