BOILERS FOR STATIONARY ENGINES.

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been often pointed out, and in consequence the pressure ought tobe lowered, or new boilers introduced, after they have been workingfor sixteen or seventeen years. Before testing, all the brick flueswere taken down, so that easy access could be got to all parts ofthe boiler, but it was left sitting on its natural seat. The boilerswere filled with water of about 120° temperature, and a force-pumpwas then attached. To check off the pressure no fewer than fivepressure-gauges were used, four of which nearly indicated the samepressure and tallied with the safety valves. At 80 lbs. pressure persquare inch an examination was made, and all appeared to be right;but as soon as the pump was started again the joint of the safetyvalve was blown out, and this stopped proceedings for a time.After this joint had been made good the pressure was again broughtup, and at 85 lbs. the joint of the feed-pump pipe, at the front endof the boiler, began to leak, owing to the bulging out of the end.At 100 lbs. a number of the longitudinal seams of the shell beganto exude water badly. The pressure was then removed, and theends gauged above and below the flues, and on the pressure beingagain put on the foilowing was the result:—Front end blow fluesbulged out in centre T S F inch at 35 lbs. pressure; ^4 inch at 100 lbs.pressure; front end above flues bulged out in centre inch at35 lbs. pressure, inch at 100 lbs. pressure; back and below fluesbulged out at centre inch at 35 lbs. pressure, F 5 F inch at 100 lbs.pressure. The pressure was then brought up to 105 lbs., when thering seam at the back of the taper of the left-hand flue began tocrack, and the pump became unable to keep up the pressure, owingto the great leakage. This joint or seam when gauged, beforetesting, measured 2 feet 3^ inches horizontally, by 2 feet 5 inchesvertically; and it gave way by crushing inwards on the flat or hori-zontal side, and remained flattened after the pressure was takenoff. This boiler was then removed, and sent to the foundry forbreaking up.

Mr. Carmichael proceeded to clear away the brick flues fromthe sister boiler. On the 15th December, 1869, it was tested in thesame way, having been in use for rather more than nineteen years.The flues were gauged, and were found, with one exception, similarto the other boiler. The exceptional one being 1 % inch oval, itwas attempted to support this flat part by fixing a batten in theline of the shortest axis of the ellipse, but this was not found tobe of any use, as the plate bulged, oozed out below at one end of

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