to the boiler; would therefore recommend that the fire should be contained in the interior of the boiler, and that there should be an additional safety-valve, which should be solely subject to the superintendance of the proprietor, and that the manager of the machine should have no possible access to it.-Would certainly recommend a wroughtmetal boiler in preference to a cast-iron boiler; and the reason was clear, that the operation of casting, however skilfully managed, was always an uncertain process.→ Thought that if an additional safety-valve was applied to a boiler, and that safety-valve placed beyond the power of being interfered with by any person but the proprietor, then the boiler would be secure from explosion, if the safety-valve should be judiciously loaded; but if the safety-valve was even placed beyond the reach of the operator, and at the same time injudiciously loaded, a calamity might take place, the same as if no such security existed. -Under all the circumstances of the case, would most decidedly recommend a condensing engine; a condensing engine, with a wrought-iron boiler; because, when cast iron became subject to high expansion and contraction, the constant repetition of those effects in a very great degree impaired the strength of the boiler.-Would venture to say, that all engines in steam-boats should be subject to regulation and inspection by competent persons.

A steam-boat must have a register; and, before such a register should be granted, the engine should be inspected, to see whether it was of a character to deserve its being considered safe.-Was quite satisfied, that, taking for granted that condensing and high-pressure engines were judiciously formed, the one would take as much fuel as the other, and there would be no material saving, if any; but if two principles were associated together, as in the case of Woolf's engine, there would be a considerable saving.

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Mr. JOHN BRAITHWAITE, of the New Road, Fitzroy Square, Engineer, called in and examined. With respect to high-pressure steam, would engage to make a boiler, or direct one to be made, which would defy any engineer, or other person, to blow up, or burst; and had lately erected five boilers, which he was ready to prove to any gentleman, and even to any engineer, that they could not destroy them. -Recommended to Mr. Martineau, for whom he erected them, that, as there had been an accident in his neighbourhood, he ought to have a boiler to bear three times the pressure he meant to put upon it; and, if it did bear that pressure, and they applied two safety-valves, with a mercurial steam-gauge properly weighted and adjusted (one of those safety-valves being at the will of the person about the boiler, and the other locked up) it would be impossible to explode a boiler of that description.-Saw the boiler after it was exploded at Wellclose Square; and also conversed with one of the men that was saved, who said, that he had carried an additional weight to put on the safetyvalve just before it exploded; that the mercurial gauge there was plugged up, so that it was useless; besides which, instead of the safety-valve being weighted equal to forty-five pounds, they added a double weight, which increased it to ninety-pounds weight upon an inch, and the boiler was very improperly made.-Would recommend wrought-iron boilers in preference to cast, on board of steam-boats.

Mr. JOHN HALL, of Dartford, Engineer, called in and examined. Had only to observe, that he made his boilers of cast iron, and proved them by an hydraulic press, made for the purpose; and had gone as high as two hundred and fifty pounds to an inch, which he considered enough. Nothing happened; and he meant the next time to try what they would bear; and had no doubt they would bear from

seven hundred to one thousand pounds to an inch; for he believed they could be made stronger than wrought-iron boilers; wrought-iron boilers being rivetted together, could not be so strong as those cast in a solid mass.-Had a boiler made composed of three tubes on a large one, and two smaller ones below; the lower tubes which were exposed most to the fire, had cracked, generally by cooling, after the engine had done working. Had known that in three or four instances; perhaps in an hour after the engine had done working, the tubes below had cracked, and the other not.-Supposed that in the event of explosion the greatest danger would be from the wrought-iron boiler.

-Considered it quite practicable to adjust a safety-valve to a boiler, which should not be accessible to the engineer, but which should sufficiently protect the boiler from mischief, and which once adjusted, would always act, and might always be depended upon.

Mr. ALEXANDER TILLOCH, of Islington, called in and examined. Was of opinion, that attending to what should be attended to in every steam-engine, and employing proper engineers, a steam-engine would be perfectly safe, whether with high-pressure or low-pressure steam. The boilers ought always to be furnished with safety-valves, one of which should be covered, and out of reach, with a box over it, but perforated, so that it might be seen when the steam operated on it. A mercurial-valve is also very good, that is, an inverted syphon, with a column of mercury, proportioned to the purposes for which it is to be employed. -Did not apprehend much danger to arise, in case of explosion, from the mercury, because the tube being always perpendicular, the mercury, when shot out, would fall down in rain. Was of opinion a boiler might be made safe, either of wrought or cast iron; but, for great strain, would prefer cast iron, contrary to the opinion of many

people; and the reason for this preference was the same for which it was preferred in making cannon. It was not possible to get thick plates of wrought iron perfect throughout, and it was necessary to trust at last to rivets in joining them; but cast-iron boilers could be made of any strength. Instead of having a boiler that would stand sixty, it might be made to stand six hundred of either wrought or cast iron. Another reason why he would prefer cast iron was, that the sheet iron corroded much quicker, and was destroyed by oxydation, so that a boiler might be safe when first set up, and stand its proof, but very soon become unserviceable, or at least, comparatively So. Boilers should always be cylindrical, and for an obvious reason: capacity should be got by length and number, rather than by diameter. There was no more danger to be apprehended from steam, as to bursting, than from the employment of condensed air, only that the water might scald: but, as to the danger of the fragments being scattered about, it was the same with air as with steam, and yet all the engineers constantly employ cast-iron receivers, condensers, or air-vessels, where pressure was wanted. In case of actual explosion, should think the greatest mischief would arise from the cast-iron boiler.→ Was aware that there might be cavities in cast-iron, but a boiler being proved to a strain beyond that it was to be exposed to by heat, the safety of the boiler was secured, for the temperature never could be at that point which would endanger a fracture from that circumstance.

Mr. GEORGE DODD, Civil Engineer, of Oxford Street, stated, that out of five steam-boats under his direction, only two had suffered by partial accidents, and these were owing to the carelessness of the engine workers. His boilers were made flat sided, with flat and dome roofs, the largest of them containing at least fifteen hundred rivets,

each of which in some measure answered the purpose of a safety-valve. Was of opinion that to all boilers there should be two safety-valves. The one which would be accessible to the engine worker should be loaded with the minimum of the pressure that the chief engineer saw fit that the boiler should sustain; and that the one which would be inaccessible and locked up, should be loaded equal to the ultimatum that he would, under any circumstances, permit the boiler to support. Would not allow the safety-valves to be loaded with more than half the weight which had been previously tried, and found the boiler was capable of supporting.-Was of opinion that a boiler whose sides and ends were flat, if properly constructed, and of sufficient thickness in the plates of wrought iron, might be safely used on board steam-boats having the low-pressure engine. In the Richmond steamboat the fire was entirely surrounded by the water. It was the case also in the Majestic; but, in the Thames, and in the new boat to Richmond, and the new boat to Gravesend, they were what was called open furnace-mouths. Under the furnace-mouth was placed an ash-hole of cast iron, bedded in clay, and upon fire-bricks.-Recollected the boiler of the Caledonia, London and Margate steampacket, bursting at sea, by the forcing out of three of the rivets over the furnace-mouth, which extinguished the fire; but it was not productive of any injurious consequences to any of the persons on board; and the Cork and Cove packet-boat in Ireland, with two hundred and fifty officers and soldiers on board, burst her boiler when lying alongside of the transport that was receiving the troops. The bursting made a fissure, or opening, of nine inches by eighteen inches; but the steam which escaped did no injury either to the persons on board or to the vessel; nor does it appear, under any circumstances of the bursting of