steam cock a shade to warm the glass, and when it is hot enough, open it more and commence closing the blow-out cock, by tapping it lightly by hand, then open the steam cock a little more and open the water cock a little also, and shut off the blow-out cock, and presently the water enters the glass, and both top and bottom cocks may now be opened to their full extent, and the job is done.

7. Question.—How would you cut a water gauge-glass to the proper length?

Answer.—I usually cut a piece of iron wire the length the glass should be, in this way: I measure the length from under the top nut to the top of the bottom nut, and cut my iron wire to that measurement; then I cut several glasses in my spare time, instead of doing it when the glass breaks. I mark a circle where I wish to cut the glass, and with a three-corner file I run it round this circle to a depth of the 16th of an inch, and break it off on the edge of the vice, bench, or other solid woodwork; of course this iron-wire gauge will perhaps only answer for this particular boiler, but in some stoke-hold the boilers are all alike with regard to the gauge-glasses.

8. Question.—What is the cause of a vacuum in a boiler? And how does it affect her injuriously?

Answer.—The vacuum is mostly caused by letting cold water into a hot boiler, the hotter the boiler the stronger the vacuum; when the water is hotter than the boiler, there will be little vacuum; a strong vacuum in the boiler will cause the air outside to press on the boiler in proportion—the stronger the vacuum inside, the greater the pressure outside. In this circumstance the pressure is misplaced for the boiler was constructed to bear an internal pressure and not an external pressure. And in getting steam up the pressure on the boiler has to be reversed, and this tends to loosen the plates and rivets and makes her leak, if she never leaked before. I have frequently known boilers to be filled with water over-night to be ready for lighting up in the morning, and have found the gauge-glass empty; this puzzled me at first, but on opening the blow-out cock of the water-gauge the air rushed into it with a gurgling noise, then I knew there was water in the boiler held up by the vacuum, but I soon altered that by opening the side-cocks, and letting air into her which soon killed the vacuum, and down came the water into the glass again to the proper level. When getting steam up, I always open one of the side gauge cocks and keep it open until steam issues from it; that permits the foul air to escape and prevents a vacuum being created; there used to be a vacuum valve in the vicinity of the steam dome, that opened inwards and prevented a vacuum from being created.

9. Question.—If you had only one boiler and one engine at work, how would you manage to clean your one fire without letting the steam go down?

Answer.—When pushed for steam, which usually occurs when the fire is getting dirty, I get ready all the tools and some of the best of the coals, and having a bright fire I take the long poker and skim all the fire to one side and throw a couple of shovelfuls of coals evenly over it and rake out all the clinkers on the opposite side, then with the long poker (some people call it Kennedy) I skim all the fire over to the opposite side and throw a couple of shovelfuls of coals evenly over the bright fire, and rake out the clinkers on the other side, then I spread the fire evenly over the bars and sprinkle some more coals over all, and shut the door. This performance from first to last need not take more than ten minutes, and the boiler was making steam all the time, and at the finish I had a better fire than at the beginning, and the steam hardly lost a pound; but the job must be done quickly.

10. Question.—What is the cause of the humming noise that issues from a steam boiler at times, and how would you prevent it?

Answer.—It is caused chiefly through bad stoking, in having an uneven fire, full of holes, or crooked bars, the cold air rushing through where there is the least resistance, and into the tubes, causes the humming noise—a locomotive nearing home after her day's work has very little fire on the bars and will generally hum, so there is some excuse for her, but none for a stationary boiler. Some stokers take credit to themselves for making the boiler "Hum"; when coals are thrown into the fire indiscriminately—small and large—the air finds the least resistance through the small coals, which soon burst into holes, while the lumps remain solid; then the air rushes into the holes and the humming commences; or, if the firebars are not equally separated, the air enters the widest space and the boiler hums; or it may be that the bars next the side of the fireplace are out of line and lets the air rush up against the side and the boiler hums. If the stoker would only drop a shovelful of coals dexterously into each hole the humming would stop immediately, or level the fire with the rake or long poker, or open the fire door if the rake is too heavy, and the noise will cease. The chief point is to have a good set of firebars and well placed; if they are too long they will hump in the middle or they will bulge sideways; if they are too close together they become red-hot because there is not room enough for the air to pass between them to keep them moderately cool, and if they are too short they will drop down into the ash-pit.

11. Question.—Why is it more difficult to keep steam-tight the manhole cover of a portable boiler than the manhole cover of a stationary boiler?

Answer.—The portable cover is usually on the side of the boiler, and about half the cover is immersed in the water and half in the steam; the portion under water is about 212° of heat, the portion of the same cover in the steam is about 500° of heat, the hottest part expanding much more than the cooler part, and is constantly tending to tear itself away from the lower portion of the cover, and the joint cannot stand the unequal strain. The manhole cover of a stationary boiler is nearly always on top of the boiler, and the heat is equal all over it and no contraction and expansion to cause the joint to leak as in the portable cover.

12. Question.—How would you prepare a boiler for the inspection of a boiler inspector?

Answer.—I would blow her right out, take off the manhole cover, take out the safety valve, take out all firebars and the bridge, take down flue-port brickwork, have the boiler and flues thoroughly cleaned and swept, have a lamp or candle ready to light, a hand hammer and chisel, or scraper, a pailful of clean water, and a wad of cotton waste. When the inspector arrives, he quickly dons his overalls; I hand him the light and the tools and waste, and he is into the fireplace in a jiffy; down the side flues, under the boiler, giving a whack with the hammer now and then, and scraping off any suspicious scale, etc.; and when he comes out, as black as any sweep, he slips out of the overalls, gives them a whack against the wall, folds them up tight, and crams them into the black bag; has a dive in the pail, and is soon ready to go off somewhere else. But he tells me something about the boiler before he goes—not to my discredit.

13. Question.—How do you proceed to get her to work again, and what materials do you use?

Answer.—I first proceed to build the bridge and flue-ports, put in the firebars, the thin bars at the sides; then I replace the safety-valve, taking care not