cooling surface, which the Patentees were not allowed to remedy. They, therefore, removed the pipes, although the Proprietors were willing to continue their use until the new machinery preparing for the vessel was fitted. That the plan did answer, is in evidence by the two years' working of it applied to the "Dragon" on the same terms, and approved of by the Directors of the Company to which she belongs. But what were the consequences of the removal of the pipes from the "City of Londonderry?" Certainly not a little singular, nor could there be better evidence afforded of the importance of the invention. A vessel that made five or six successive passages across the Bay of Biscay, in the worst period of the year, keeping her post-office time with Symington's condensation attached, was, on the two successive voyages next after the pipes were removed, unable to make the passage in time, for want of steam, though at a finer period of the year; and, shortly afterwards, she ceased to be employed in the Government service at all. The "City of Londonderry" was never tried after she was lengthened, until the pipes were attached, and thus, unfortunately for the Patentees, faults were attributed to the pipes that arose from inadequacy of power to the alteration, or other causes, afterwards ascertained by her inability to keep her time immediately this mode of condensation was discontinued. She then burnt and salted her boilers to such an extent, that her fuel was more speedily consumed, and she could not get a sufficiency of steam. There can be no better evidence of the assistance she derived from the plan, and the saving in fuel, than this fact. When the pipes were being removed, they were found to be as sound and as fast as when first applied. On the voyage after the pipes were removed, and the engineer was unable to get a sufficiency of steam, the vessel being in some difficulty in consequence, he observed to the captain, "This would not have occurred if we had had Symington's condensation."

The facts proving the advantages of this method of preventing incrustation, as applied to this vessel, are in evidence by the certificates of her engineers, and may be seen on application to the Patentees. One of the engineers thought so highly of it, that he has everywhere recommended it, and it has since been applied to another vessel, in which it answers beautifully.

To show, in addition to the case of the "City of Londonderry," how difficult it is to introduce a new invention, and upon how slight a cause it may be condemned, independent of its merits-Whilst the last vessel was being fitted, some unprincipled fellow, careless of the consequences, so that he injured the invention, had filled the injection-pipe with tow, and thus, when set a-going, the engine would work neither with the old nor new plan. The proprietor wrote that the pipes were to be immediately removed, stating he had been deceived in the assurance that the old plan would not be interfered with. Satisfied that what had answered during two years could not fail, a careful examination led to the discovery of this shameful attempt at injury. The new plan was immediately turned on, and, when tried against the old, always increased the revolutions of the wheels from 31 to 37. The Proprietor was quite satisfied with it!

To meet objection—and it is better to do so, however unnecessary the pipes on this vessel were protected by a very fine, though strong, projection of about half an inch beyond them, above and below, and finely rounded at the sides. This makes them completely embayed; and they are thus represented in the drawing, to show that nothing can reach them applied in this manner. There was, however, no protection to the "City of Londonderry's" pipes, and yet they received no injury. Of so little value is experience, and so powerful is fanciful opinion.

The second boat to which the plan was applied, was

the "Dragon" tug, of 60-horse power, working at a pressure of from ten to twelve pounds on the square inch, which pressure greatly increases the difficulty of cooling. The error upon the first trial was provided against, success was complete, and the plan now equals every expectation.

It was applied to the "Dragon," as before stated, upon the same terms as to the "City of Londonderry”—that the Patentees were not to be paid for it unless approved of. The Directors of the Company to which the "Dragon" belongs did approve of it. They have had it in constant work for nearly two years, exposed to every variety of trial, that the Shareholders might not pay for an unprofitable invention. They have found a constant saving in fuel, of nearly onethird, and, since the copper pipes were substituted for zinc, which were found would not stand the ice, the boilers have not been once cleaned or chipped. When the "Dragon" was employed towing a vessel from the Helder to Dunkirk, and thence returned to London, the same saving in fuel was observed; the coals were carefully weighed, and her time noted: the boilers were not blown out once, and they were examined a few days ago, and reported to be as clean as when they came from the maker's hands. During the two years this plan of condensation has been used, the boilers have cost nothing for repairs, while another tug, whose boilers were new about the same time as the "Dragon's," have cost the same Company, in the same period, more than £200, besides her loss for detention. That tug is only thirty-five horse power, the "Dragon" two thirties; her boilers, therefore, at the same rate, and in the same time, would have cost double, had not this mode of condensation been applied. The "Dragon" has been employed in work more likely to incrust her boilers than the other tug.

Although this is a fine boat, she is the only one of her form in the river, and the most unfavourable in shape that could

be selected for the safety of the pipes; yet they have stood two years' constant hard work and knocking about of a tug, exposed to the obstructions of a densely crowded river, and barges swinging against her, uninjured; liable, from peculiar formation, to double the danger they were in on the "Londonderry." Sufficient trials have, therefore, been made to prove that no danger can attach to these pipes, that does not attach in an equal degree to the keel, and to every part of the vessel from the keel to light-water mark; and, as before stated, it is only reasonable to conclude, that unless done for the purpose, they can receive no damage. A few spare pipes on board would enable any injury to be far more speedily repaired than the serious accident to the vessel, which would alone render it necessary; and as no damage could be done to the one without the other, both might be repaired at the same time. In the Report on Steam Vessel Accidents, it is stated that in the City of Dublin Steam Shipping Company, “each vessel is placed on the gridiron at least once in every three months, merely to sight her bottom;" so that the pipes would be under sufficient inspection, though, once properly fastened, they would last just as long without looking to as the sheathing of the vessel. This Company presents one of those gratifying instances of British capital and enterprise, to be found nowhere but in this country. They possessed, in 1839, a fleet of 21 sea-going steamers, amounting to nearly 9,500 tons, of the united power of 5,550 horses, and crossed the channel 1,800 times a year. The amount of trade carried on by this one Company must be very great.

CHAPTER IV.

ACCIDENTAL DISCOVERY OR REVIVAL OF CONDENSATION BY INJECTION, IN 1711.-MR. WATT'S EXPERIMENTS.-LETTER TO MR. SMEATON, GIVING THE PREFERENCE TO AN INJECTION.-GREAT AUTHORITY.-CONDENSATION BY SURFACE AND BY INJECTION.- DISADVANTAGES OF THE FORMER.-PAPERS ON THE TWO SYSTEMS, IN MECHANICS' MAGAZINE.— SYMINGTON'S INJECTION SELF-REGULATING.

LIKE many other valuable combinations, we owe to accident the beautiful discovery of the affinity of steam for water. Newcomen's engine continued to be worked by surface-condensation until about the year 1711, when the workmen were astonished one day to see the piston travelling with unwonted rapidity.* Unable to account, upon any known principle, for what they had never seen before, investigation led to the discovery of the cause. The piston, in that age of the Steam Engine, was always covered with water, as the best packing then known to adapt itself to the irregularities of the bore of the cylinder; the means of boring the cylinder true, at that period being undiscovered. The piston was found to be pierced, by accident, in many places; through these holes the water found its way, and, falling upon the steam in a continued jet, condensed it with so much greater rapidity than by surface, that, from that day, condensation by surface was superseded, and, with the exception of some experiments tried by Mr. Watt, entirely suppressed, until its revival three

* See "Mechanics' Magazine," No. 882, p. 78.