PREPARATIONS FOR ANOTHER ATTEMPT
"Taking Stock"--Further Capital--Alterations in Paying-Out
Machinery--Improved Testing and Signaling Apparatus.
This untoward interruption to the expedition was naturally a cause of
great disappointment to all connected with the undertaking; for there
was not enough cable left to complete the work, nor was there time to
get more made and stowed on board to renew the attempt before the season
would be too far advanced.
The squadron proceeded to Plymouth to unload the cable into tanks at
Keyham (now Devonport) Dockyard, chiefly because some of the ships could
not be spared by their respective governments till the following year.
In the middle of October (1857), the engineer-in-chief proceeded to
Valentia in a small paddle-steamer with the object of picking up some of
the lost line from this end. After experiencing a series of gales, over
fifty miles of the main cable were recovered, and the shore end buoyed
ready for splicing on to in the coming year.
The first expedition had opened the eyes of the investing public to the
vastness of the undertaking, and led many to doubt who did not doubt
before. Some began to look upon it as a romantic adventure of the sea,
rather than as a serious commercial undertaking. This decline of
popular faith was felt as soon as there was a call for more money. The
loss of 335 miles of cable, with the postponement of the expedition to
another year, was equivalent to a loss of £100,000.
[Illustration: FIG. 15.--Reshipment of the Cable aboard H.M.S. Agamemnon
and U.S.N.S. Niagara in Keyham Basin.]
_Raising Further Capital._--To make the above sum good, the capital of
the company had to be increased, and this new capital was not so readily
obtainable. The projectors found that it was easy to go with the current
of popular enthusiasm, but very hard to stem a growing tide of popular
distrust. And it must also be remembered that, from the very first, the
section of the public which looked with distrust upon the idea of an
Atlantic telegraph was far in excess of that which did not; indeed, the
opposition encountered was much on a par with the great popular
prejudice which George Stephenson had to overcome when projecting his
great railway schemes. But whatever the depression at the untimely
termination of the first expedition, it did not interfere with renewed
and vigorous efforts to prepare for a second. In the end the appeal to
the shareholders for more money was responded to; and the directors were
enabled to give orders for the manufacture of 700 miles of new cable of
the same description, to make up for what had been lost, and to provide
a surplus against all contingencies. Thus, 3,000 nautical miles in all
were shipped this time, instead of 2,500 miles.
_Alterations in the Paying-Out Gear._--New paying-out machinery was
devised with a view to obviating the possibility of a recurrence of the
accident on the first expedition. In the new apparatus the brake (Fig.
16) was so arranged that a lever exercised a uniform holding power in
exact proportion to the weights attached to it (Fig. 17); and while
capable of being _released_ by a hand-wheel, it could not be tightened.
The general idea of this clever appliance had been originally introduced
by Mr. J. G. Appold in connection with the crank apparatus in jails; and
it was now especially adapted to the exigencies of cable work by the
engineer (Mr. Bright) and Mr. C. E. Amos, a member of the famous
engineering firm, Easton & Amos, who constructed the entire machinery.
The great future of the apparatus was that it provided for automatic
brake-release, upon the strain exceeding that intended. Thus, only a
maximum agreed strain could be applied, this being regulated from time
to time by weights, according to the depth of water and consequent
weight of cable being paid out. In passing from the hold to the stern of
the laying vessel, the cable is taken round a drum, or drums. Fig. 18
gives a general view of the apparatus. Attached to the axle of the drum
is a wheel fitted with an iron friction-strap (to which are fixed blocks
of hard wood) capable of exerting a given retarding power, varying with
the weights hung on to the lever which tightens the strap. When the
friction becomes great, the wheels have an increased tendency to carry
the wooden blocks round with them; thus the lever-bars are deflected
from the vertical line and the iron band opened sufficiently to lessen
the brake-power.
[Illustration: FIG. 16.--The Self-Releasing Brake.]
[Illustration: FIG. 17.--The Principle of the Brake.]
Bright also introduced a dynamometer apparatus for indicating and
controlling the strain during paying out--a vast improvement on that
embodied in the previous machines. The working of the entire machine was
as follows:
"Between the two brake-drums and the stern of the vessel, the cable was
led under the grooved wheel, O, of the dynamometer. This wheel had a
weight attached to it, and could be moved up or down in an iron frame.
If the strain upon the cable was small, the wheel would bend the cable
downward, and its index would show a low degree of pressure; but
whenever the strain increased, the cable, in straightening itself, would
at once lift the dynamometer-wheel with the indicator attached to it,
which showed the pressure in hundredweights and tons. The amount of
strain with a given weight upon the wheel, G, was determined by
experiments, and a hand-wheel in connection with the levers of the
paying-out machine was placed immediately opposite the dynamometer; so
that, directly the indicator showed strain increasing, the person in
charge could at once, by turning the hand-wheel, lift up the weights
that tightened the friction-straps, and so let the cable run freely
through the paying-out machine. Although, therefore, the strain could be
_reduced_--or entirely withdrawn--in a moment, it could not be
_increased_ by the man at the wheel. The cable in coming from the tanks,
passed under a lightly weighted 'jockey,'[22] J, pulley. This
arrangement, while leading the line on to the drums, at the same time
checked it slightly. From here it was guided by a grooved pulley, or
V-sheave,[23] L, along the tops of both drums, at B, then three times
round them, and hence over another V-sheave, F, and on to the
dynamometer. From this the cable was led over a second pulley, and so
into the sea by the stern-sheaves."[24]
This entire apparatus--simplified as regards the brake--has since been
universally adopted for submarine-cable work,[25] with the exception
that a single-flanged drum, fitted with a sort of plow, skid, or
knife-edge--to guide or "fleet" the incoming turn of cable correctly on
to the drum--is now used in place of the grooved sheave, or sheaves.
As soon as the new machinery was constructed, all the engineering staff
gathered together for the purpose of thoroughly acquainting themselves
with its working. Mr. F. C. Webb, having engagements elsewhere, had been
replaced by Mr. W. E. Everett, U.S.A., who had been chief marine
engineer of the Niagara. Mr. Everett was to have charge of the machinery
on the laying vessel, while Mr. Woodhouse controlled the cable
operations.
[Illustration: FIG. 18.--Bright's Paying-out Gear, 1858.]
_Alterations in the Electrical Apparatus._--Since the manufacture of the
cable in 1857, Professor Thomson had become impressed with the
conviction that the electric conductivity of copper varied greatly with
its degree of purity. As a result of the professor's further
investigations, the extra length of cable made for the coming expedition
was subjected to systematic and searching tests for the purity and
conductivity of the copper. Every hank of wire was tested, and all whose
conducting power fell below a certain value rejected. Here, then, we
have the first instance of an organized system of testing for
conductivity at the cable factory--a system which has ever since been
rigorously insisted on.
_Professor Thomson's Mirror Instrument._--And now, in the spring of
1858, an invention was perfected that was destined to have a remarkable
effect on submarine-cable enterprise. For Professor Thomson (now Lord
Kelvin) devised and perfected the mirror-speaking instrument, then often
described as the marine galvanometer,[26] of which it may be fairly said
that it entirely revolutionized long-distance signaling and electrical
testing aboard ship.
This most ingenious apparatus consists of a small and exceedingly light
steel magnet (_a_) (Fig. 19) with a tiny reflector or mirror fixed to
it, both together weighing but a single grain or thereabouts. This
delicate magnet is suspended from its center by a filament of silk and
surrounded by a coil (_b_) of the thinnest insulated copper wire.
[Illustration: FIG. 19.--The Reflecting Magnet.]
A very weak current is sufficient to produce a slight, though nearly
imperceptible, movement of the suspended magnet when electricity passes
through the surrounding coil. A fine ray of light from a shaded lamp,
behind a screen (Figs. 20 and 21) at a short distance, is directed
through a slot in the screen, thence to the open center of the coil
(_c_) upon the mirror. It is then reflected back to a graduated scale
(_f_). As may be seen from Fig. 21, an exceedingly slight angle of
motion on the part of the magnet (_a_) is thus made to magnify the
movement of the spot of light upon the scale (_f_), and to render it so
considerable as to be readily noted by the eye of the operating clerk.
The ray is brought to a focus by passing through a lens. By combinations
of these movements of the speck of light (in length and direction) upon
the index, an alphabet is readily formed. The magnet is artificially
brought back to zero with great precision after each signal by the
earth's magnetism, and also both by the natural torsion of the fiber and
the controlling action of the adjusting magnet (_e_) (Fig. 20), with
the help of the thumb-screw (_d_) for regulation purposes.
[Illustration: FIG. 20.--Reflecting Galvanometer and Speaker.]
In a word, Professor Thomson's combined mirror-telegraph and marine
galvanometer transmitted messages by multiplying and magnifying the
signals through a cable by the agency of imponderable light.
[Illustration: FIG. 21.]
It is only to be regretted that the electrician responsible for the
subsequent working through operations did not sooner appreciate the
great beauties of the above apparatus, and the advantage of a small
generating force such as it alone required.