Carrying the 4000 km (2500 miles) of cable, the Great Eastern set off westward from Foilhummerum Bay on 25 July 1865. She headed toward the equally remote western end at Heart's Content, Newfoundland.
This image shows crowds of onlookers on the island of Valentia watching the great vessel depart.
The first problem came only a few hours after the Great Eastern set off from Valentia. At 3.15 a.m. the technicians' instruments showed a failure in the electrical current along the cable.
There was no reverse gear on the paying out equipment, so the cable was cut and both ends brought on board the ship. She reversed her course and recovered the cable already laid.
After travelling 16 km (10 miles), at a speed of 1.6 kilometres an hour (1 mph), the faulty section of cable was brought on board. Somehow a piece of wire, 5 cm (2 inches) long, had been driven right through the cable, stopping it from working by earthing the current.
On 29 July 1865, with 1015 km (634 miles) of cable laid, another break was shown on the instruments. Careful examination revealed that yet another piece of wire had been pushed into the cable's core.
Although it was never proved, it seemed very likely that this was a deliberate act of sabotage. This image shows the crew searching for the fault.
After the cable was repaired the laying carried on. The following days were trouble-free. But when the Great Eastern was only two days away from Heart's Content another section of faulty cable jumped out of the rollers of the cable-laying machine.
The retrieval operation was began, and as the crew were feeding the cable back into the ship's bow roller, the strain suddenly increased and the cable snapped. Now the broken end of 1600 kilometres (1000 miles) of cable lay perhaps 2000 fathoms (almost 2 km, or 1.25 miles) below on the ocean-bed.
Usually it was possible to lower huge hooks over the side of the ship to grapple for broken cables, join the ends and carry on. But this time the weather was too bad to retrieve the broken end.
The cable's position was marked with a buoy and the attempt was abandoned. The spot in mid-Atlantic was 1709 km (1062 miles ) from Valentia and 975 km (606 miles) from Heart's Content, Newfoundland. These images show the position being marked with the buoy. With the marker in position, the Great Eastern turned for home.
He launched an operation to retrieve the end of the cable from the bottom of the Atlantic some 4000 m (13,124 ft) below.
It seemed a hopeless task. But there had been successful attempts before at depths of over 1000 m (3281 ft), and the Great Eastern seamen were experienced in the procedure.
Two 150 kg (330 lbs) grapnels - five-armed anchor-like hooks attached to thousands of metres of wire rope, were lowered, as the ship drifted slowly back across the route of the cable. After two hours, instruments showed the grapnels had reached the sea-bed. This photograph shows what the hooks looked like.
Attempts were made to grapple the telegraph cable on 3 August and again on 7 August. Each time, hundreds of metres of cable were heaved off the sea bottom. But each time the joints of the wire rope broke under the enormous strain of lifting not just the weight of the cable, but also the wire rope's own weight.
The weight of lifting the cable also put huge strain on the lifting gear on deck. Repair crews had to work day and night to keep the capstans and machinery working. This image shows the crew working in the forge at night to repair damaged instruments.
During the evening of 11 August 1866, the cable was successfully lifted, even though the lifting wire had failed for the third time. Once the cable had been retrieved, the Great Eastern was able to steam on until she reached Heart's Content.