inciples enunciated by Professor Thomson. The
conductor consisted of seven wires of pure copper, weighing three
hundred pounds to the mile. This copper core was covered with
Chatterton's compound, which served as water-proofing. This was
surrounded by four layers of gutta-percha, cemented together by the
compound, and about this hemp was wound. The outer layer consisted
of eighteen steel wires wound spirally, each being covered with a
wrapping of hemp impregnated with a preservative solution. The new
cable was twice as heavy as the old and more than twice as strong, a
great advance having been made in the methods of manufacturing steel
wire.

It was decided that the cable should, be laid by one vessel, instead
of endeavoring to work from two as in the past. Happily, a boat was
available which was fitted to carry this enormous burden. This was
the _Great Eastern_, a mammoth vessel far in advance of her time.
This great ship of 22,500 tons had been completed in 1857, but had not
proved a commercial success. The docks of that day were not adequate,
the harbors were not deep enough, and the cargoes were insufficient.
She had long lain idle when she was secured by the cable company and
fitted out for the purpose of laying the cable, which was the first
useful work which had been found for the great ship. The 2,300 miles
of heavy cable was coiled into the hull and paying-out machinery was
installed upon the decks. Huge quantities of coal and other supplies
were added.

Capt. James Anderson of the Cunard Line was placed in command of the
ship for the expedition, with Captain Moriarty, R.N., as navigating
officer. Professor Thomson and Mr. C.F. Varley represented the
Atlantic Telegraph Company as electricians and scientific advisers.
Mr. Samuel Canning was engineer in charge for the contractors. Mr.
Field was also on board.

It was on July 23, 1865, that the expedition started from the Irish
coast, where the eastern end of the cable had been landed. Less than a
hundred miles of cable had been laid when the electricians discovered
a fault in the cable. The _Great Eastern_ was stopped, the course was
retraced, and the cable picked up until the fault was reached. It was
found that a piece of iron wire had in some way pierced the cable
so that the insulation was ruined. This was repaired and the work of
laying was again commenced. Five days later, when some seven hundred
miles of cable had been laid, communication was again int