From the Drawing in the Victoria and Albert Museum.
It was in this ship that a type of engine was fitted to which, so far, we have not referred. This was the oscillating kind, and was destined to become pretty well universal in paddle-ships, though not without serious opposition at one time. This type had been patented as far back as 1827, by Joseph Maudslay, and in the Aaron Manby, already mentioned, the machinery was of an oscillating nature, for which Manby had obtained a patent in 1821, but even farther back still—in 1785—William Murdoch had proposed the use of oscillating cylinders. It is only fair to Maudslay to say that he had independently worked out this arrangement, and so afforded yet another instance of the possibility, which I have enunciated before, of different inventors working at the same set of problems and bringing about a similar method of solution. [In the accompanying illustration] is shown Maudslay’s original oscillating engine. In this type the cylinders, instead of being fixed, oscillate, and the necessity of the connecting rod is dispensed with, for the cylinder is placed immediately underneath the crank shaft, as a reference to the illustration will show. Each cylinder is mounted on trunnions in the same manner as a cannon, being placed at a point about the middle of the cylinder’s length, so that it can swing, or oscillate, in such a way as to correspond with the arc which the crank makes in its movement. Thus there are both weight and valuable space saved. In the instance before us the condenser is placed between the two cylinders; the central trunnions communicate with the condenser, and the outside trunnions with the steam pipe. But Maudslay’s engines did not at that time find the appreciation which had been hoped for, and it was not until 1838, when they were re-introduced by John Penn, that they received their full favour. We shall return to the oscillating type when we come to consider the Great Eastern. But we may remark that the interesting steamship illustrated [opposite page 130] was also provided with the oscillating pattern. This is the packet steamer Pacific, which was built in 1853 for the Mediterranean service, and is another example of a vessel constructed on the wave-line system. She was built of iron, and had nine water-tight compartments.
The Pacific was interesting in another feature, in that she generated her steam in four tubular boilers, each of which had five furnaces. Briefly the evolution of the boiler had been on this wise: As originally fitted in the Clermont and Comet it was simply a water-tank set in brickwork, and was nearly full of water, with the fire outside, or, to use the expression generally employed, “externally fired.” In those days the pressure of the steam was not greater than the pressure of the air, which we saw to be 15 lb. to the square inch. Then came a modification of this in which the furnace was placed inside the boiler, the advantage being that, with the water all round, the latter could be the more readily heated. This developed into the marine “box” boiler, with internal flat-sided flues and furnaces. This type continued to be fairly universal until about 1845, but the utmost pressure of steam which these were capable of enduring was not above 35 lb. or thereabouts. But tubes instead of the flat flues began to be introduced about the year 1850, owing to the suggestion of the Earl of Dundonald, and these were to be of about double the diameter of those which had been common to locomotives for the previous twenty years. The pressure was soon raised considerably, but there was a strong prejudice against using high pressures at sea, and the idea was not encouraged.
THE “VICTORIA” (1852).
From the Model in the Victoria and Albert Museum.
THE “HIMALAYA” (1853).
From the Model in the Victoria and Albert Museum.
