U2 Air VduU of the Devon Iron Works, 



When the furface was put in blaft, after having been filled with coakcs, and gently 

 heated for more than fix weeks, the keepers allowed it to have but little blaft at firft, 

 giving it a fmall blow-pipe of about 2~ inch diameter, and likewife letting off a very con- 

 Cderabl© quantity of air, at the efcape, or fafety valve on the top of the iron wind cheft, 

 as it is a received though erroneous opinion among them, that the blaft muft be let on very 

 gradually for feveral months. From the conftru£tion of this valve, it was impofRble to afcer- 

 tain the exadl: proportion of the blaft they thus parted wich, but I believe it was very 

 confiderable. The confequence was, that the furnace, after it had been in blaft for feveral 

 days, never feemed to arrive at its proper degree of heat, but was always black and cold 

 about the tweer in the hearth, and appeared in danger of choking, or gobbing, as it 

 is termed. 



After various experiments tried in vain, by the keepers and the company's engineer, 

 and others, (indeed they tried every thing, except giving the furnace a greater quantity of 

 air, which, as I afterwards afcertained, was all that it wanted), they concluded, that the 

 air vault was the caufe of the whole mifchief; and, to confirm their opinion, they faid 

 they had now difcovered that water was, in confiderable quantities, driven out of the air 

 vault through the blow-pipe, which cooled the furnace ; and they infifted, that the power 

 of the engine was fuch as to force water out of the folid rock ; fo that this method of 

 equalizing the blaft never would fucceed. The other managing partner was fo much 

 alarmed by thefe reprefentations, that he began to confult with the engineer, and others, 

 about finding a fubftitute for the air vault at any expence. 



As the plan of the bloviring apparatus had been adopted at my recommendation, and 

 was now fo loudly condemned jsn account of the water, I had other motives, than mere 

 intcreft, for trying to become better acquaintad with the phxnomena attending it. I ac- 

 cordingly determined to go into the air vault, and to remain inclofed in the condenfed 

 air while the engine was blowing the furnace. It is an experiment that perhaps never was 

 made before, as there never exifted fuch an opportunity. I could not perfuade the 

 engineer, or any other of the operative people about the work, to be my companions, as 

 they imagined that there was much danger in the experiment. Mr. Neil Ryrie, however, 

 one of the clerks of the Devon company, had fufficient confidence in my reprefentations 

 to venture himfelf along with me. 



The machine had been ftopped about two hours previous to our entering the vault, and 

 we found a dampnefs and miftinefs in it, which difappeared foon after the door was (hut 

 faft upon us, and the engine began to work in its ufual manner. After four or five ftrokes 

 of the engine, we both experienced a fingular fenfation in our ears, as if they were ftopped 

 by the fingers, which continued as long as we remained in the condenfed air. Our 

 breathing was not in the leaft afFedled. I had no thermometer with me, but the tem- 

 perature of the air felt to us the fame as that without the vault. Sound was much mag- 

 nified, as we perceived, when we talked to each other, or ftruck any thing ; particularly, 

 .the noife of the air efcaping at the blow-pipe, or waftc valve, was very loud, and fejemed 



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