The machinery also was perfected in every part, to withstand the great strain which might be brought upon it in grappling and lifting the cable from the great depths of the Atlantic. This necessitated almost a reconstruction of the machinery, together with engines of greater power, applied both to the gear for hauling in forward and that for paying out aft. Thus, in case of a fault, the motion of the ship could be easily reversed, and the cable hauled back by the paying-out machinery, without waiting for the long and tedious process of bringing the cable round from the stern to the bow of the ship. But the most marvellous improvement had been in the method of testing the cable for the discovery of faults. In the last expedition, a grave omission had been in the long intervals during which the cable was left without a test of its insulation. Thus, from thirty to thirty-five minutes in each hour it was occupied with tests of minor importance, which would not indicate the existence of a fault, so that, if a fault occurred on ship-board, it might pass over the stern, and be miles away before it was discovered. But now a new and ingenious method was devised by Mr. Willoughby Smith, by which the cable will be tested _every instant_. The current will not cease to flow any more than the blood ceases to flow in human veins. The cord is vital in every part, and if touched at any point it reveals the wound as instinctively as the nerves of a living man flash to the brain a wound in any part of the human frame. The process of detecting faults is too scientific to be detailed in these pages. We can only stand in silent wonder at the result, when we hear it stated by Mr. Varley, that the system of testing is brought to such a degree of perfection, that skilful electricians can point out minute faults with an unerring accuracy "even when they are so small that they would not weaken the signals through the Atlantic cable one millionth part!" Another marvellous result of science was the exact report obtained of the state of that portion of the cable now lying in the sea. The electricians at Valentia were daily experimenting on the line which lay stretched twelve hundred and thirteen miles on the bottom of the deep, and pronounced it intact. Not a fault could be found from one end to the other. As when a master of the organ runs his hands over the keys, and tells in an instant if it be in perfect tune, so did these skilful manipulators, fingering at the end of this mightier instrument, declare it to be in perfect tone, ready to whisper its harmonies through the seas. At the same time, the ten hundred and seventy miles of cable left on board the Great Eastern were pronounced as faultless as the day they had been shipped on board.