114 0'^ ^'^^ various KffeSls produced by 



When fuch confequences arife from the tranfition fo fre-; 

 qucnt in winter from froft to thaw, it will be eafily con- 

 ceived that the change effcfted during the milder and 

 warmer months muft produce proportionally additional ef- 

 fefts. The increafe of temperature by taking up, and hold- 

 ing in folution, a much greater portion of aqueous vapour, 

 will account for the ordinary efiefts which are annually ob- 

 fervable in every \york. Where thefe pernicious confequertces 

 approach to extremitv, a folution of the phenomenon wilj 

 likely ht obtained bv the exaniinatjon of the blowing-appa- 

 ratus. If air is fitted for combuftion in proportion as it i? 

 free from watery folutions, we are not to expeft fiuailar re- 

 itilts from thefe blaft-fiirnaces in fummer, which are blowri 

 by air from the regulating cylinder, and thofe blown by air 

 from a water or air- vault. I have for years feen this faft 

 ytrified, and fuperior quantity and quality of iron during the 

 hot weather, obtained from a furnace excited by means of 

 blaft, from the fimplc regulating cylinder, with a lefs pro- 

 portion of fuel than from furnaces whofe air was expreflTcd 

 by means of the water or air-vault. Obfervations thus made, 

 where every day the effefts of the diffefcnt means cquld be 

 juftly cftimated and compared, have led me to the following 

 conclufion : That the quality of the air, as furniflicd us by 

 nature in our atmofpherc, is uniformly niore tit for the ma- 

 . nufafture of crude iron to profitable account, when difcharged 

 limply by means of cylinders and piftons, than when brought 

 into coatadt with moifture either in the water-vault or air- 

 vault. 



So impcrfcft has the quality of the fummer air been found 

 i.T this country for combiiftion, where tlic water-vault was 

 ufed, that experiments have been made to repair the defi- 

 ciency of effett by introducing fteam into the furnace by means 

 of an aperture above the tuyre. The inducing motive to this 

 aft, was a belief, that combuftion was diminifhed in confc- 

 quence of a diminution of oxvgen gas during the fummer; 

 that, by introdtcing water upon a furface of materials ignitccf 

 to whitenefs, decompofition would enfue, a larger quantity of 

 oxygen would then be prcfcnted to the fuel, and fuperior 

 ffleits, as to combuftion, obtained in this manner than hi- 

 therto 



