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Appendix .

hour were consuming upon the grate, the bars were seldom sohot as to discolour writing paper, when pressed against them.Secondly, another effect, of considerable importance in Lon­ don , was that the fire-bricks which formed a part of the fire-place were not even vitrified, and would therefore last verymuch longer than in the usual furnace. Thirdly, the boilers,in consequence of the regularity of the heat, might fairly beexpected to last much longer, and the supplementary boiler,on which of course the greatest wear would take place, mightat any time be taken down, while the principal boiler, withall its connecting pipes, remained unmoved.

In the fire-regulator, first, by the very equal distributionof the coal upon the surface of the grate, a thin fire anda sharp draught was maintained, and this was effected bythe coal being introduced in small quantities falling uponthe whole of the area of the fire in regular succession. Se-condly, the coal was introduced upon the fire without open-ing the fire-door; and this was effected by dropping thecoal through the roof of the supplementary boiler. Thirdly,the decomposition of the coal was much more perfectthan by the common furnace, and this was effected by therevolving of the grate, which exposed each side of everypiece of coal on the grate to the current of the fire passingconstantly in one direction across it. Fourthly, the intro-duction of the coal was completely governed by the steamgenerated, analogous to a water-wheel, governing by its ve-locity the quantity of the water permitted to fall upon it;thus, considering the production of the steam as the effect,and the introduction of coal as the cause, the former had aperfect check over the latter, and at no time admitted morecoal into combustion than was really necessary for the per-formance of the work which the engine was then doing.Fifthly, the whole apparatus, being a very simple mechanicalarrangement, acted independently of either the skill or the