40 SCIENCE IN SHORT CHAPTERS. 



By this simple arrangement we get a firegrate with a narrow 

 flat back and out-sloping sides ; all these three walls are of 

 fire-brick ; the back radiates perpendicularly across the room ; 

 and the sloping sides radiate outward, instead of merely across 

 the fire from one to the other, as when they are square to the 

 walls. 



At Rumford's time our ordinary fireplaces were square 

 recesses ; now we have adopted something like his suggestion 

 in the sloping sides of our register grates, and we bring our 

 fireplaces forward. We have gone backward in material, by 

 using iron, but this, after all, may be merely due to the iron- 

 mongery interest overpowering that of the bricklayers. The 

 preponderance of this interest in the South Kensington Exhibi- 

 tion may account for the fact that Rumford's simple device 

 was not to be seen in action there. It could not pay anybody 

 to exhibit such a thing, as nobody can patent it, and nobody 

 can sell it. I have seen the Rumford arrangement carried out 

 in office fireplaces with remarkable success. To apply it any- 

 where requires only an intelligent bricklayer, a few bricks, and 

 some iron bars. 



Although nobody exhibited this, a very near approach to it 

 was described in an admirable lecture delivered at South Ken- 

 sington, by Mr. Fletcher, of Warrington. In one respect Mr. 

 Fletcher goes further than Count Rumford in the application 

 of fire-clay. He makes the bottom of the fire-box of a slab of 

 fire-clay instead of ordinary iron fire-bars. This demands a 

 little more trouble and care in lighting the fire, owing to the 

 absence of bottom-draught, but when the fire is well started 

 the advantages of this further incasing in fire-clay are consider- 

 able. They depend upon another effect of the superior radiant 

 and absorbent properties of fire-clay that I will now explain. 



So far, I have only described the beneficial effect of its radia- 

 tion on the room to be heated, but it performs a further duty 

 inside the fireplace itself. Being a bad conductor, it does not 

 readily carry away the heat of the burning coal that rests upon 

 it, and being also an excellent absorber, it soon becomes very 

 hot i.e. superficially hot, or hot where its heat is effective. 

 This action may be seen in a common register stove with fire- 

 clay back and iron sides. When the fire is brisk the back is 

 visibly red hot, while the sides are still dull. If, after such 

 fire has burned itself out, we carefully examine the ashes, there 

 will be found more fine dust in contact with the fire-brick than 

 with the iron i.e. evidence of more complete combustion 



