30 Transactions. — Miscellaneous. 



all until it reached a surface formed by an absorbent body, such as our oxidized 

 iron, which is capable of receiving the heat vibrations, which receptive surface 

 can then heat the air above it. 



Now, as the small amount of aqueous vapour in our atmosphere is the 

 main absorber of radiant heat, thus allowing the diathermanous air to become 

 heated, which heated air can then be conveyed to distant parts b}'' winds ; so 

 also can a minute admixture of the compound molecules of various gases — 

 such as those fx-om coal — greatly pi'omote the heating of air for blast fui-uaces. 



It is evident that in this manner the heat vibrations alone can be 

 transferred from one tube to the other, wliile their gaseous contents are 

 prevented from mixing. If a revolving fan be the means adopted for 

 circulating the gases, it can be applied to any convenient pai^t of the circuit of 

 either of the tubes a or b. In the figure it is connected with A, and therefoi'e 

 first draws the fresh and heated air, and then discharges it under pressure into 

 a large and bx-oad tube extending close aloxig the bottom of the boiler, and 

 thence into a I'eservoir dix'ectly below the fux-nace and boilex', which supplies 

 the tuyeres with the heated aix'. The thermo-coxivector axid connections there- 

 from are covered with felt, and then cased with tin, leaviixg an air space 

 between . 



The outlet of the tube B conveys the waste and cooled gases downwax'ds 

 over a shallow vessel of water (c), thus arresting the ashes, which speedily 

 sink, and the gases can escape there for locomotives (which would be an 

 important desidei'atum in tunnels and underground x'ailways), or be conveyed 

 over the ship's side in marine engines, or else made to go upwards thi'ough a 

 funnel by the pressure of the blast. This funxiel is useful in fix-st getting up 

 the fire, for which pux-pose the door t> is lowered, which then closes the 

 tube B. 



As there is a coxisiderable amount of water in some bx'owxi coals, and as 

 this would have a tendency to condense in the tube B and thus airest the 

 ashes, it was necessaiy to deterrxnne the tempex-atux-e at which its vapour 

 would condense, axid I find that if 10 per cent, of water exist in the coal, its 

 vapour will not coxidense uxitil it is lowered to 27° F., which gives a sufiicient 

 margin to ensure a dxy exit to the ashes. 



It has been shown by Joixle and Mayer that the mechanical force ax'ising 

 from heating lib. of water 1° F. is equal to raising 7721bs. one foot high. 

 When we therefore consider the exiorinous quantity of air xiecessary to px-omote 

 combustioxi of the fuel (oxie ton of coal requiring about 448,000 cubic feet, or 

 more thaxi 15 tons), and, further, that this immense volume of air requix-es its 

 tempex'ature raising to that of the bux'xiing fuel, it is evident that a veiy great 

 saving can be efl^ected by heatixig it before it exiters the fux'nace, for it matters 

 not on what part of the absolute scale this 1^ increase occurs, let it only be 



