40 PHENOMENA ohjervtd in the AIR VAULT.' 



ly increafed. It continued to be, on an average of nine 

 months immediately after this improvement, at the rate of -^Ti 

 tons of iron per week, of as good quaUty as formerly ; for 

 dm'ing this period, from the 21ft November 1795 to July 30. 

 1796, this one furnace yielded 1188 tons of iron. No more 

 coals were confumed in working the blaft engine, or other ex- 

 pences about the blowing machine incurred, and therefore no 

 more power was employed to produce this great efFeifl. It 

 is alfo of much importance to remark, that the confumption of 

 materials, from which this large produce was obtained, was by 

 no means fo great as formerly. The furnace required very con- 

 fiderably lejs fuel, lefs ironjlone, and lefs limejloiie, than were em- 

 ployed to produce the fame quantity of iron by the former me- 

 thod of blowing ; and according to the ftatements made out by 

 the Coinpany's orders, as great a change was effedled in the 

 ceconomical part of the bufinefs. 



From the fuccefs of this experiment, fo well authenticated, and 

 continued for feveral months, I am led to be of opinion, that all 

 blaft furnaces, by a proper adjuftment of fuch machinery as they 

 are provided with, might greatly and advantageoufly increafe 

 their produce, by affuming this as a principle, viz. " That zvith 

 the given power it is rather by a great quantity of air thrown into 

 the furnace, with a moderate velocity, than by a lefs quantity thrown 

 in with a greater velocity, that the greatefl benefit is derived, in 

 the f melting of ironjlone s, in order to produce pig-iron.''^ However, 

 it is by experiment alone, perhaps, that we can be enabled to 

 find out the exa<5l relations of power, velocity, and quantity of 

 air requifite to produce a maximum of effedl *. :• 



But, an unfortvinate difagreement among the partners of the 

 Devon Company, put it out of my power to make further pro- 



grefs 



* If Q^ be the quantity of a ifluid, iffuing in a given time through an aperture of 

 the diameter D, V its velocity, and P the power by which it is forced through 

 the aperture : then the area of that aperture being as D*, the quantity of the fluid 

 ilTaing in the given time will be as VD^, or VD' = Q^ 



Again, 



