38 PHENOMENA obferved in the AIR l^AULT 



from the knowledge I had acquired from my father Dr RoE- 

 nucK, and from my communications -with other experienced 

 iron maftcrs, that a great part of the power of fuch machinery 

 was mifapplied in general praclice, by throwing air into fur- 

 naces with much greater velocity than necelTary, and that, if 

 this velocity was, to a certain degree diminifhed, the fame 

 power, by properly adjufting the blowing machinery, of what- 

 ever nature, would be capable of throwing into the furnace a 

 proportionally greater quantity of air. For, " Since the quan- 

 tities of any Jluid, iffuing through the fame aperture, are as the 

 fiuare roots of the preffure ;^^ it follows, that it would reqiiire 

 four times the preffure, or power, to expel double the quantity of 

 air, through the fame aperture, in the fame time : But if the 

 area of the aperture was doubled, then the quantity of air ex- 

 pelled by the fame power, and in the fame time, would be in- 

 creafed in the ratio of the fquare root of 2 to i, though its ve- 

 locity would be diminiflied exadlly in the fame proportion. 

 Again : I confidered that the quantity and intenfity of heat, 

 produced in blaft furnaces, and confequently its efFe<fls in in- 

 creafing the produce, might be only in proportion to the quan- 

 tity of air decompofed in the procefs of combuftion, without 

 regard to its greater velocity ; that is to fay, whether or not 

 the fame quantity of air was forced, in the fame time, into 

 the furnace through a fmall pipe, or through one of larger 

 dimenfions ; for, in attending to the procefs of a common air 

 furnace for remeklng of iron, where there is a very large quan- 

 tity of air admitted through the large [areas between the bars, 

 it is well known, that a much greater intenfity of heat is pro- 

 duced than takes place in a blaft furnace, and yet the air does 

 not enter into the fire through the bars with increafed den- 

 lity or great velocity. I therefore thought it probable, that in- 

 creafing the quantity of air, thrown into the blaft furnace in a 

 confiderable degree, although the velocity or denfity might be 



much 



