safety-valve does not lift at the pressure it ought to lift at I know that the valve is sticking, and I lift the lever and let the steam out; the cause of the sticking may be that the valve has worn down in its seat and becomes conical, or there may be a shoulder on the valve that would cause it to stick, or it may be that the lever and fulcrum were smeared with oily dirty waste in the process of cleaning and not wiped off, but left to bake between the parts, which would prevent the free action of the safety valve.

20. Question.—Why is the safety-valve lifted at times, especially when getting steam up?

Answer.—It is often done by old stokers as well as new ones, and is more of a silly habit than of trying the pressure of the steam, especially as there is nowadays a pressure gauge for every boiler in a stoke-hold. By lifting the safety-valve while steam is in the boiler and dropping it down again is a dangerous practice; there is a rush of steam to the valve when lifted, and when it drops the rush of steam is instantly stopped, and rebounds like an india-rubber ball hit against the wall, and this commotion within the boiler is likely to blow the stop-valve to pieces or the manhole cover off. Besides that, there is always dust floating on the surface of the water, especially in a boiler just cleaned, and when the valve is lifted the dust is carried up with the steam, and when the valve is dropped the dust is caught under it and often causes the valve to leak.

21. Question.—When the water in the gauge-glass appears motionless while the boiler is working, what does it portend, and how would you proceed to rectify the stagnation of the water?

Answer.—It portends that the passage for the water is choked and requires clearing, and I would lose no time in commencing to rectify the stoppage; as a stoker who is responsible for the safety of the boiler I am always prepared for emergencies. I commence by shutting both cocks of the glass, the steam and the water, and unscrew the small bolt in the water gauge, which is fixed there for the purpose of clearing the tube that conveys the water to the glass, and with an iron wire in one hand, I open the water cock with the other hand, and push the wire into the small hole from which I took the bolt, giving several pushes and pulls while the water and steam are flying out, until the tube is quite clear; then I withdraw the wire, shut the cock, and serve the steam cock in like manner; and while I was doing all this the bottom cock of the gauge (the blow-out cock) was open from the beginning. Then I commence to put the pressure on the glass by warming it with steam from the top cock slowly; then I open the water cock a little, and so on, alternately; then I commence shutting the blow-out cock a little. By these manœuvres the pressure on the glass is put on gradually instead of popping it on too suddenly and breaking the glass, as is often done by the more-haste-the-less-speed stoker; now I shut the bottom cock and open the other two, and the water bounds into the glass quite frisky, and the boiler is safe for the present.

22. Question.—What would be the consequence if the steam cock of the water gauge was choked, while the water cock was clear, or vice versa?

Answer.—The consequence would be most serious for the boiler, as the water would be forced up into the glass by the steam under it, and would make it appear as if too much water was in the boiler, and the stoker would proceed in the usual way to blow out some of this, apparently, surplus water; and then watch to see it come down to the working level in the glass, but he watches in vain—it will never come down. He might empty the boiler dry, and the water in the glass will be there as long as a breath of steam remains in the boiler to keep it up. And in the event of the water-cock being choked while the steam-cock was clear the consequence would be equally dangerous, for the water that was in the glass before the stoppage occurred would remain in it, for the stoppage would not allow it to drop down into the boiler again; so there it would remain, and when the stoker came round to look at his boiler, unless he happened to notice that no movement of the water was visible, he would pass on without further ado, and remain in total ignorance of his danger. Hence the necessity for the stoker to blow out his water gauge every time he comes in front of his boiler, and if the water enters the glass in a sluggish or dilatory way the cocks need to be cleared of the partial stoppage, and let the water enter the glass with a rush.

23. Question.—Could a boiler collapse without affecting the fusible plug?

Answer.—Yes; the tank that supplied the boiler with water leaked badly, and to stop the leaks a quantity of fine oatmeal was mixed with water and poured into it, and in due time reached the boiler; but instead of the oatmeal permeating the whole of the water in the boiler, it never got beyond the parts surrounding the fireplace; it stuck on the sides and top thickly, and was baked hard on them. After a few days the sides of the fire-tube bulged inwards nearly twelve inches, and the boiler had to be stopped and blown out, and the fusible plug was found to be unaffected—it was one selected by a Boiler Insurance Company, who had to repair this damage, and the stoker was exonerated from blame, but there is little doubt that if the plug had leaked the mishap would have been attributed to shortness of water and the stoker would be blamed for what he did not do, and get the sack into the bargain.

24. Question.—Why is it that an injector can force water into a boiler from which the steam comes to work the injector at a greater pressure than is in the boiler?

Answer.—The secret of the working of the injector is due to the velocity of the steam issuing from the point of a conical tube, and water issuing from another conical tube somewhat larger than the steam cone, and a partial vacuum created in the barrel by the steam and cold water meeting—as both cones face each other. The cones are about four inches long, one and a quarter inch wide at the mouths, and about one half of an inch at the points. The suction pipe, steam pipe and delivery pipe are about one inch diameter, and the overflow pipe half an inch diameter, and the water tank three feet below the level of the injector, the space within the barrel might be twelve square inches; the water and steam cocks are supposed to be always open, and this is how the injector is started working. The water-wheel is turned partly round, and a figured disc behind it indicates the quantity of water let into the barrel, while the steam is let in by turning a wheel attached to a quick-screw spindle; then there are ructions inside—the steam and water have come together, and the water overflows through the half-inch pipe; but by a little manipulation of the water, air will soon start it working; then the overflow ceases, and the air rushes into the pipe and hums, and the injector is working. And the reason of its working is, in my humble opinion, the concentration of water and steam, with the vacuum thrown in, that gives additional pressure to the water in the injector. I might venture to say it gives fully ten lb. on the square inch over and above the pressure of steam within the boiler.

25. Question.—The noise created by the injector while working being very objectionable, could it be mitigated? And, if so, how?

Answer.—Yes; I succeeded in quieting an injector in one establishment