[107] At this period, Mr. Rennie, who planned the breakwater at Plymouth and new London Bridge, was “advising engineer” to the Admiralty, and on every occasion urged the application of steam-power to vessels of war. More than this, he hired at his own cost the Margate steam-boat, the Eclipse, and successfully towed the Hastings, 74, against the tide from Woolwich to Gravesend, June 14th, 1819. On this the Admiralty, supported by Lord Melville, gave up their objections.—Smiles’ “Lives,” vol. ii. p. 267.
[108] William Denny, the builder of the Rob Roy, as also of the Marjory (noticed [p. 75]), was born in Dumbarton in 1789, where his forefathers for some generations had been “wee lairds” (yeomen) farming their own land. After serving his apprenticeship as a joiner and ship-carpenter, and acting as manager of a small ship-building yard on the River Leven, Dumbarton, he commenced business on his own account at that place, and was the first to lay down in his yard Morton’s patent slips, where he built various sailing-ships for the East and West India trades. He died in December 1833. Three of his sons, also, William, Alexander, and Peter, commenced business at that place as iron ship builders in 1844, on a small piece of ground, removing in 1847 to a larger yard, where they continued the business of iron ship builders under the firm of William Denny and Brothers, by which it is still known. In 1851, two other brothers, James and Archibald, having then joined them, they (there were seven brothers, all shipbuilders) commenced the business of engine builders, subsequently adding to this that of founding and forging, so that all the branches of work connected with steam shipbuilding might be done on the spot. William was a man of remarkable genius and talent, and attained so high a reputation as a marine architect that he and his brother Alexander planned most of the steamers built on the Clyde from 1839 to 1844. He died in 1854, and the only brother now left is the youngest, Mr. Peter Denny, who, with his son and Mr. Walter Brock, carries on this well-known and extensive business, which, in the years 1873 and 1874, built and fitted with engines 37,000 tons of iron screw-ships. Since 1844 the town of Dumbarton has risen, almost entirely through their exertions, from a population of 4000 to 12,000 inhabitants. But, beyond his fame as an iron ship builder, Mr. Peter Denny is known in public life, having been appointed a member of the Royal Commission in 1872 of which the Duke of Somerset was Chairman, to inquire into the cause of the loss of life and property at sea.
[109] In this vessel Mr. Napier introduced, for the first time in England, a plan for surface condensation; the condenser was composed of a series of small copper tubes, through which the steam passed towards the air-pump, and a constant current of cold water encircling the pipes, the steam was cooled and returned into water, which was again sent into the boiler for conversion into steam, without being mixed with the cold salt water, which, in the usual plan, was injected into the condenser. But, like Watt, Cartwright, and others who had tried this system, both here and in America, Mr. Napier finding the rapidity of condensation not sufficient, returned to the old system of condensation by jet. Some years afterwards, however, he reverted to the use of a surface condenser under peculiar circumstances, which rendered it desirable to use flat plates instead of tubes, but the advantages of the system have not been considered sufficient to counterbalance the disadvantages. The first engine of Bell was to some extent a vertical engine, inasmuch as the axis of the cylinder and of the crank were placed in one vertical line; but there was no direct connection between the cranks and the piston-rod, to the paddle-axle: the communication of motion to it, being effected through the medium of toothed wheels. In the common or lever engine, the piston-rod acts on a cross-head, the cross-head on side rods, the side rods on side levers, the lever on a cross-tail, the cross-tail on the connecting-rod, the connecting-rod on the crank-pin, by which, through the axle, the paddle-wheels revolve. In the engine of direct communication, the side levers and some other parts of the train of communication are removed by a device which enables the piston-rod to be almost immediately attached by a connecting-rod to the crank of the paddle-shaft. This plan was first adopted by Mr. Gutznur, of Leith, who built the Athol, and another vessel called the Tourist, on this principle: but as his method, though very simple, was not applicable in ordinary cases, Mr. Napier made several modifications, so that his vertical engine, in the judgment of the most competent engineers, includes almost all the best improvements as yet introduced.
[110] In an able pamphlet, “The Fleet of the Future,” by Mr. Scott Russell, published by Longman & Co. in 1861, the author remarks (p. 20), “A good many years ago I happened to converse with the chief naval architect of one of our dockyards on the subject of building ships of iron—the answer was characteristic, and the feeling it expressed so strong and natural that I have never forgotten it; he said, with some indignation, “Don’t talk to me about iron ships, it’s contrary to nature.””
There was at one time almost as great a prejudice against Indian teak as a material for ship-building, as this wood is heavier than water, and in the form of a log will not float. (Arnott, “Elem. of Physics,” p. 305.)
[111] See “Rolls’ Chapel Reports,” 7th Report, p. 204.
[112] See “Repository of Arts,” vol. xxviii. (second series), p. 138, and Woodcroft’s “Specification of Marine Propulsion,” Part I. p. 63, and “Steam Navigation,” p. 125.
[113] Fincham’s “Naval Architecture,” on the use of iron for shipbuilding.
[114] William Laird, father of the late John Laird, M.P., established the Birkenhead Iron Works in 1824, under the style of William Laird and Sons, and, in 1829, they built for the Irish Inland Company the first iron vessel constructed on the Mersey. She was a lighter of 60 tons measurement, about 60 feet long and 13 feet beam. From that time until 1861, Mr. John Laird carried on this extensive business of shipbuilding and engineering, and when, in that year, he was elected to represent Birkenhead in Parliament, he transferred it to his sons, who now carry it on under the style of Laird Brothers.
Mr. Laird died in October 1874, about the same time as Sir William Fairbairn, another distinguished worker in the field of applied science, and both men of great eminence in their profession.