Note 109 — Chapter II

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.