238 Account of Mr. Walker's improved 



and two feet wide. On the top of this case are apertures at 

 certain distances, suppose twelve or fifteen feet, which open 

 and shut at pleasure, to permit the escape of the heated air. 

 The iron flue is conducted into the end of the case from the 

 furnace, which is placed in the usual manner in a stoke-pit, 

 on the outside, and a few feet lower than the floor of the 

 house. To the end of the case, where the flue enters, there 

 is an air-flue conducted upwards from the bottom of the 

 stoke-pit, where its oiifice is provided with a valve to shut, if 

 required, but this is rarely, if ever, necessary. At this opening 

 the supply of air enters, and being healed as it passes along 

 in contact with the iron flue, escapes uirough the apertures 

 in the top of the case, and mixing with the atmosphere warms 

 the house. Here the ingenuity of the contrivance may be 

 particularly remarked in the arrangement of the current of 

 air; for, this current having its commencement when cold at 

 the part of the flue which is hottest, it takes up the heat there, 

 where it is least wanted, and carries it to those purts at a dis- 

 tance from the furnace where it is most needed ; and as the 

 valves will be chiefly opened in the latter situations, to per- 

 mit its escape, it diffuses a nearly equal warmth over the 

 whole house. 



This apparatus is similar in many respects to that of 

 Mr. Ken i,* and though the latter was entirely unknown 

 to Mr. Walker, it is evident that he had in view the 

 principles whereon it is fuunded. The chief advantage com- 

 mon to both is, that the case, or coffer, intercepts the radi- 

 ance of the heat, and provides a store of heated air, which 

 being conveyed away from the immediate neighbourhood of 



• S«e Horticultural Transactions, vol. ii. p. 389. 



