56 A SAGA OF THE SEAS 
found quickly. Sir John, with genuine British courtesy, re- 
plied that his Government was pressed for ships to convey 
troops to Malta, but he would see what he could do. In an 
hour or two he sent word that Her Majesty’s ship Valorous 
had been ordered to replace the Susquehanna. The Gorgon 
was replacing the Leopard of the year before in the British 
arrangements. 
There was over three thousand miles of cable to load on 
the Niagara and the Agamemnon. ‘This included a new 
length of seven hundred miles and a thirty-nine mile piece 
that had been recovered from the lost cable of the year be- 
fore. Placing the cable on the two ships was a task of no small 
difficulty. A hundred and sixty men, divided into four groups 
to relieve one another, labored day and night during all of 
April and most of May. The cable had to be coiled carefully 
on large cones to avoid injuring the insulation. 
Preliminary tests were conducted in the Bay of Biscay, in- 
cluding splicing and lowering the cable and electric conti- 
nuity. ‘The new mirror “galvanometer” invented by William 
Thomson was carefully tested. ‘This replaced the Morse sys- 
tem with its familiar relays, and eliminated momentum and 
inertia by a delicate needle and a tiny mirror to reflect a ray 
of light. This was only one of the many services of Professor 
Thomson to the work. At this time, he insisted upon very 
pure copper being used in the cable and kept the tests to a 
high standard. Not only was he a good theorist; he had prac- 
tical Scottish sense. Years later he invented the slender needle 
that is still seen in cable offices tracing ink-marks on a ribbon 
of tape, and which replaced the mirror galvanometer. 
A new plan of procedure in the cable-laying was to be 
tried at this time. Instead of starting the work from the coast 
of Ireland, the two ships carrying the cable were to meet in 
mid-ocean, splice the two halves together, and sail apart, one 
for Ireland and the other for Newfoundland. This method 
had been favored by Bright the year before, but the other 
