228 THE SCIENTIFIC PAPERS OF 



brickwork at each end of the furnace per pound of coal burned in 

 the gas-producer per hour would be theoretically sufficient to 

 absorb the waste heat, if the whole mass of the regenerator were 

 uniformly heated at each reversal to the full temperature of the 

 flame, and then completely cooled by the gases coming in ; 

 but in practice by far the larger part of the depth of regenerator 

 chequer-work is required to effect the gradual cooling of the 

 products of combustion, and only a small portion near the 

 top, perhaps a fourth of the whole mass, is heated uniformly 

 to the full temperature of the flame ; the heat of the lower 

 portion decreasing gradually downwards nearly to the bottom. 

 Three or four times as much brickwork is thus required in the 

 regenerators, as is equal in capacity for heat to the products of 

 combustion. 



The best size and arrangement of the bricks is determined by 

 the consideration of the extent of opening required between them 

 to give a free passage to the air and gas, and by the rule, deduced 

 from my experiments on the action of regenerators in 1851-2,* 

 that a surface of six square feet is necessary in the regenerator to 

 take up the heat of the products of combustion of one pound of 

 coal in an hour. 



By placing the regenerators vertically and heating them from 

 the top, the heating and cooling actions are made much more 

 uniform throughout than when the draught is in any other 

 direction, as the hot descending current on the one hand passes 

 down most freely through the coolest part of the mass, while the 

 ascending current of air or gas to be heated, rises chiefly through 

 that part which happens to be hottest, and cools it to an equality 

 with the rest. 



The regenerators should be always at a lower level than the 

 heating chamber ; as the gas and air are then forced into the 

 furnace by the draught of the heated regenerators, and it may be 

 worked to its full power, either with an outward pressure in the 

 heating chamber, so that the flame blows out on opening the doors 

 or with the pressure in the chamber just balanced, the flame some- 

 times blowing out a little, and sometimes drawing in. The out- 

 ward pressure of the flame prevents that chilling of the furnace, 



* Proceedings of the Institution of Civil Engineers, 1852-3, page 571, " On 

 the Conversion of Heat into Mechanical Effect. " 



