INTRODUCTION OF STEAM AND IRON A revolution in the history of the ship may be said to have occurred with the changes from sails to steam engines for propulsion and from wood to iron for construction. These pro ceeded together, but at first very slowly. Conservative tendencies in many quarters, notably at the British Admiralty, strongly re sisted the introduction of the steam ship, while the marine engine itself was undoubtedly somewhat imperfect and extravagant in fuel in its early stages. As already stated, there was still much ignorance of the principle of flotation by displacement, and it was urged by the unenlightened that iron would not float and was therefore unsuitable for ship construction. Even amongst those who realised the fallacy of this argument it was asserted that an iron ship would be far more easily damaged in the event of her touching the ground than a wooden one, while there existed the very real difficulties of preserving the bottom from the action of the sea and fouling by weeds and barnacles, and of compensating the compass for the errors produced by local at traction. With regard to the strength of the ship, experience showed that iron construction was better able to withstand rough usage than wood, and examples were not lacking of iron and wooden ships being stranded together by the same gale and under similar circumstances and the iron ship getting off little the worse, while the wooden ship became a total wreck. A remark
able instance of the endurance of iron ships was that of the "Great Britain," which, in 1846, ran ashore in Dundrum Bay in Ireland and settled on two detached rocks; she remained aground for eleven months, was subsequently got off, and afterwards did good service. In due course a suitable composition was dis covered for painting the underwater surface of iron ships, while trials carried out in the "Rainbow" at Deptford and the "Iron side" at Liverpool went far towards providing the solution for correcting the compass.
One of the earliest iron craft on record was a boat apparently intended for passenger service, built on the banks of the river Foss in Yorkshire in 1777. In 1787 a canal lighter was con structed with a shell of iron plates, and for many years iron and wood were used in conjunction for the construction of what were known as composite ships.
For warships iron was at first objected to because it was thought that the enemy's shot would cause more serious damage to them than it would to a wooden ship, but this again was proved to be a fallacy.