144

DIEECT EETUKN TUBULAR ARRANGEMENT.

especially for the reception of the steam. Thetubes also are raised higher from the base linein this case than in that of previous allusion,doubtless for the purpose of forming a recessin the combustion chamber, below the lowerrow of tubes.

Thus far the exceptions are disposed of, andthe next step is the description of the arrange-ment in question. On noticing the transversesectional elevation, it will be seen that the toprow of tubes is above the crown of fire boxes ;

for the ordinary twofold purpose of preventingadhesion and permitting an escape of steam ata lower pressure than required to lift the valvenaturally, due to the load on the same.

The other sectional elevation representsthe combustion chamber, smoke box, anduptake in section. The tubes connecting thetwo former, it is noticed, are at an. incline, forthe purpose of accelerating the draught. Therecess, already alluded to, below the bottom rowof tubes, is for the reception of soot, &c., that

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also the crown of the combustion chamber issimilar. The sections given of the fire boxesare centrally of the length and at the frontend, to show the width in each instance. Thedoors seen under the grate, at the back ends,are for the admission of air beyond the bridge,a suitable framework being fitted in the firebox. The stays are situated according to theirseveral requirements; disconnection beingattained by the removal of the pins or cotters.The gear shown in the dome, and that in dottedlines below it, relate to the safety valve, being

passes from the furnace during imperfect com-bustion/

The smoke box is in two compartments, fromthe base to the upper row of tubes, where aconnection is lormed, and the uptake thus ren-dered common to both sets of tubes. This isa contrast with Fig. 17—page 115—where isshown, in sectional plan, that each smoke boxis separate, in front of the tubes.

In the view now under direct notice, theuptake is curved, the steam thereby surround-ing it, which renders partial super-heating