Air nfed In the "Blajl-Vurnace. bj 



fiifficiently known by the effefts which it produces in the 

 blaft-furnace, and ought to be fubjedl to fcrupiilous examine 

 ation. 



In this, as in other countries, larger produces of caft iron 

 are obtained in the winter months than during the famnier 

 and autumn feafons : the quality of the metal is alfo much 

 more carbonated, and with a lefs proportion of fuel. In 

 many parts of Sweden, where the fummer heats are intenfe, 

 the manufafturer is obliged to blow out or flop his furnace 

 for two or three months : not only is he unable to make 

 carbonated metal, but is frequently incapable of keeping the 

 furnace in fuch trim as to make a produce of any quality 

 whatever. In Britain, during the months of June, July, and 

 Auguft, more efpecially in dry feafons, the quality of the iron, 

 with the local proportion of fuel, will be depreciated ^o per 

 cent., and the quantity reduced to 2-3ds or 3-4ihs. 



In feeking for a folution of this univerfally acknowledged 

 faft, our attention is naturally direfted to an examination of 

 the various ftates of air. That the quality of the air in winter 

 is more fit for combuftion than in fimimer, is a truth which 

 requires no farther demonftration. Greater coolnefs, whereby 

 an almoft complete refrisjeration of moifture takes place, and 

 the prefence of perhaps a greater relative proportion gf" oxy- 

 gen, may account for this phenomenon. On the contrary, 

 the quality of air during the fummer months becomes much 

 contaminated for combuRion, by holding in folution a much 

 greater quantity of moifture : the abundance of nitrous par- 

 ticles may alfo diminifli the ufual proportion of oxygen. 



This will account for the inferior efi'cfts of combuftion 

 both in common fires and in the blaft-furnace ; it will alfo 

 in a great meafure tend to folve the curious phenomenon of 

 pig-iron taking up lefs carbon in fummer, although reduced 

 with a fuperior quantity of fuel. The air difcharged moft 

 probably contains lefs oxygen; yet the metal is much lefs 

 carbonated than at other times, when contrary proportions 

 of thefe exift. Moft probably the deficient carbon is carried 

 off by diflblving in hydrogen, forming a conftant ftream of 

 hydro-carbonic gas, while the oxygen that is fet free unites 

 to the iron j and while it reduces its quality, at the fame time 

 K 2 ' the 



