MANUFACTURE OF BOILERS.

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explained, fitted to the steam-pipes, for retaining any moisture thatis carried along with the steam, more especially steam that has notreceived a sufficient degree of superheat. The reader on turning backto page 46 will find the use of the Separator fully explained. As thepipes are made of copper, which is a very good conductor of heat, itis necessary to clothe them with feit, and then cover them over withcanvas, securely sewn together; the whole is then painted, to pre-sent a neat and smooth surface. The steam is still further treatedin the cylinder by the use of a steam jacket encircling the cylinderin all parts where radiation takes place; even the ends and the coversof the cylinders are steam-jacketed, and are still further protectedwith feit, covered with “lagging,” the technical term for narrowstrips of wood that are firmly secured to rings of wood bolted to thecylinder, ribs being cast on for that purpose. Thus it becomesimperative that pipes and surfaces, exposed to external cold, shouldbe thoroughly protected to prevent condensation or reduction ofsteam pressure. The boilers are likewise covered with feit and woodlagging, and sheet-lead Overall, to prevent radiation.

MANUFACTURE OF BOILERS.

In all branches of industry there are certain methods betteradapted for carrying on work than others, and although one makermay adopt a very different method from another, they may beequally successful in turning out as good work, although the onemay have expended more money than the other in doing so. Some,for instance, adopt modern improvements, and their plant is ofmodern make; the punching machine, for example, being supersededby the multiple drilling machine, and no one can doubt for a mo-ment that drilling the holes for the rivets is done without strainingthe plates so much as with the multiple punching machine forcingthrough three holes at once, even although the drilling machine maybe doing twenty holes at one time. The plating for boilers andother work is now done with mathematical exactness; the distancebetween the rivets for ordinary boilers, having inch rivets forsecuring the plates, is 2 inches between centre and centre, andfrom the edges 1 inch to the centres of the holes; consequentlythe plates should be ordered with even dimensions.