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REPORTS OF THE "VOLCANO" STEAM VESSEL. 229

respect efficient. In August, 1841, the report states that the performance of the vessel was in every respect satisfactory, except as to speed. A similar report was made in September. 156. Reports of the "Volcano" Steam Vessel.—The "Volcano" was built and equipped at the same time as the Megæra," and by the same manufacturers, the Messrs. Seaward, of Limehouse. The " Megæra" was furnished with the patent condenser of Mr. Hall, the "Volcano" with common injection engines. The monthly reports of the performance of the latter vessel, from February to September, inclusive, for the year 1840, are favourable :-" The engines are well constructed, and the bearings well adjusted, and are in good repair, and would no doubt answer very well for some years to a vessel of 500 tons. Had she power equal to 1-3rd of her tonnage, would be a very efficient vessel; but, with her present power, will not steer, blowing hard, against a heavy head sea. The boilers will, no doubt, last well for seven years, with the addition of new side plates to the fireplace." In November, 1840, it is stated in the monthly report that the pipes are generally defective, viz. blow-off pipe, injection pipes, bilge pipes, blow-through pipes, &c. The boilers appear, also, to have been out of repair at this time. A survey was accordingly held, and the boilers were found so defective in the take-ups as to require to be sent to England for repair. The vessel was accordingly sent home for repair in January, 1841. It is right, in giving these brief notices of the performance of two vessels, fitted up on a different plan of condensation, to add that the boilers of the "Megara" were made of iron, those of the "Volcano" of copper. How far the comparison between the performance of the two vessels may be affected by this circumstance, remains to be decided.*

For the "Reports" of the two steam vessels, above noticed, the author is indebted to the courtesy of the Lords Commissioners of the Admiralty, who afforded him every facility for obtaining the information he desired.

230

66

VOYAGE OF THE BRITISH QUEEN."

157. Voyage of the "British Queen."-The "British Queen," the noblest vessel ever constructed for Transatlantic navigation, was provided with Mr. Hall's patent condensers. By reference to the engineer's log of this ship, during her fourth voyage from New York to London, it appears that the mercury in Bedwell's patent barometer, affixed to the engines of the vessel, stood steadily at 30 inches. Mr. Peterson, chief engineer of the "British Queen," observes: "The extraordinary vacuum produced in these engines is unrivalled by any engine or engines in the world. I believe it impossible for engines on the common plan of condensation to produce a vacuum any thing like this. The vacuum, indeed, in the best sea-going injection engines, averages only 27 inches, and the fastest river boat on the Thames never yet exceeded it. The great increase of power, derived from the use of the patent condensers, is therefore self-evident. Having had the charge of another pair of engines, fitted with Mr. Hall's condensers, viz. those of H. M. S. V. 'Megæra,' made by the celebrated firm of J. and S. Seaward and Co., and having experienced nearly the same result, I feel I should not be doing Mr. Hall justice if I did not express my firm belief, that if all the vessels in which his condensers were fitted had been properly managed and understood, the same successful results would have been the consequence. I have only mentioned the increase of power derived from Hall's condensers; but the numerous other advantages derived from their use are so well known, as scarcely to require repetition-the cleanness of the boilers, the fine condition of all the internal working parts of the engines, &c., and owing to the use of the distilled water only. The 'British Queen' went from London to New York, last voyage, and returned to London, with the same water in her boilers, and without the least addition of water even to start with. In fact, the boilers were not opened from the time of leaving London until her arriving there again, when the water was perfectly pure. I have never, in fact, seen any boilers so clean, and so free

HOWARD'S METHOD OF GENERATING STEAM. 231

from deposit of any sort. It is worthy of remark, that Mr. Hall's beautiful plan of distilling in vacuo, not only supplied all occasional waste of water, arising from steam escaping from the safety valve, &c., but also furnished a large quantity of distilled water for the ship's use." The dimensions, power, and performance, of this incomparable vessel are the following:-length from figure-head to taffrail, 275 feet; length of the upper deck, 245 feet; breadth between the paddle boxes, 40 feet; breadth over all, 61 feet; depth of hold, 27 feet; diameter of paddle wheels, 31 feet; diameter of engine cylinder, 6 feet 5 inches; length of stroke, 7 feet; power of engines, 500 horses. This vessel left Portsmouth on the 2d of March, 1840, at 12-40 p. m., and arrived at Sandy Hook on Wednesday, 18th March, at 10 a. m.; total number of revolutions, 291,850; coals consumed, 635 4 tons. She left New York on the 1st of April, 1840, at 2-30 p. m., and arrived at Spithead on Thursday, 16th April, at 6 p.m.; total number of revolutions, 263,400; coals consumed, 613 tons 16 cwt.*

158. Howard's method of generating Steam.—A new method of generating steam was introduced a few years ago by Mr. Thomas Howard. The novelty of this plan consists in the production of steam from the smallest possible quantity of water on a small surface, and this, without the use of a boiler. The advantages proposed by this contrivance are, considerable economy of fuel, reduction in the weight of the machinery, diminution of the space allotted to flues, absence of smoke, and avoidance of deposit and incrustation. Mr. Howard observes, in the specification of his patent, that in the ordinary method of generating steam by means of boilers, a body of water is exposed to a large surface of metal, from which it receives a comparatively low degree of heat; and

The dimensions of the unfortunate "President" varied in no great degree from those above given; her cylinder had a larger diameter, and there was a greater length of stroke. The power of her engines was that of 600 horses.

232 HOWARD'S METHOD OF GENERATING STEAM.

that, as the temperature of water bears a constant relation to the density or pressure of the steam (page 126), the rapidity of evaporation is thereby limited. In the new process of vaporization, the power of the engine is derived from the generation of steam from the least possible quantity of water on a small surface, heated to and maintained at such a temperature (about 400° Fahr.) as will vaporize the water with the utmost rapidity; the steam so formed having a high temperature, but relatively a low density or pressure, and being, therefore, capable of parting with more or less of its heat without undergoing condensation. The surface exposed to the fire is preserved from the injurious effects of a strong local heat, by the interposition of mercury; while the vaporizing surface is preserved from deposit by the continued use of the same water, as in Mr. Hall's apparatus. In Mr. Howard's engine, alcohol, or other liquids, may be substituted for water. In describing this apparatus, the mode of generating the steam will first be explained, and then the method of producing a vacuum by condensation.

(1.) The mode of generating the steam is as follows. A plate of wrought iron is placed horizontally over a fire of coke or anthracite coal, the combustion of which is regulated by a blowing apparatus; the surface of the plate exposed to the fire is about three-fourths of a square foot for each horse power of the engine. A second plate is fixed above this, at a distance of about three inches, and firmly secured to it by means of a strong ring of corresponding depth, to which the circumferences of both the plates are tightly bolted. The surface of the upper, or vaporizing, plate is increased to about four times that of the lower, or fire plate, by the insertion of shallow cups of about two inches in diameter throughout its entire surface; the cups are open above, and closed below, where they dip towards the lower plate. The intermediate space between the two plates is filled with mercury. The temperature of the mercury should never be allowed to rise above 500° Fahr., nor to fall below 350°; the combustion of the fuel is regu

HOWARD'S METHOD OF GENERATING STEAM. 233

lated for the purpose of maintaining the due temperature. Upon the upper plate is projected, at intervals, by means of a pump, a nozzle, and a valve, a small quantity of water from a hot water cistern; this water is instantly converted into steam of very high temperature; the steam is conducted into a chamber surrounding the working cylinder, where it receives additional heat from the hot air of the flues which circulates round this chamber; the steam is then directed to the cylinder valves in the usual way. This apparatus is expressly intended for working the steam expansively, the pressure being generally about ten pounds on the square inch above that of the atmosphere, and the steam cut off from the cylinder at about a third of the stroke.

(2.) The process of condensation is as follows. The steam is conveyed from the cylinder, by means of an eduction pipe, to the condenser, as in the common engine. A jet of distilled water, from a vessel purposely provided, is allowed to play into the condenser, by which means the steam is condensed, and mixed with the distilled injection water. This warm liquid is pumped out of the condenser in the usual way; it is then cooled by being conveyed through a copper worm of many coils, which is immersed in cold water, and terminates in the vessel of distilled water; it thus serves to supply the demand for injection. By entirely filling the worm, and partly filling the hot water cistern, before the engine starts, a sufficient quantity of water is provided for circulation. A still is employed for supplying any waste of water, caused by leakage, and is attached to the flue of the vaporizer. An apparatus of this kind was fitted, in 1835, to the government steam vessel Comet, which, in a trip from Falmouth to Lisbon, consumed only one-third of the amount of fuel required by this vessel when worked by the common engines; the consumption with Mr. Howard's engine being less than 250 lbs. of coke per hour, whereas with the common engines it amounted to about 800 lbs. per hour. Mr. Howard's mode of condensation may obviously be applied with equal success to the