52S Phenomena ohfenjed in the Air-Vault 



as^itated and forced out of the rock and vault by the power of 

 the blaft, as was imagined and infifted on, we gave the fignal 

 to ftop the engine. As foon as it ceafed to work, and the 

 condenfation abated, and before the door of the vault was 

 unfcrewcd, the ivhole vault, in a few feconds, became filled 

 with a thick vapour, fo that we could hardly fee the candles 

 at four or five jyards difiance. The door being now opened, 

 the work-people, anxious to know our fituation, and what 

 had occurred, came into the vault, and prevented any further 

 obfervations. I now endeavoured to account for this curious 

 appearance of the \Vater, which only (howcd itfelf occafion- 

 ally, in very fmall quantities, at the tweer, and at a hole I 

 ordered to be made in the bottom of the wind-cheft to colleft 

 it more accurately; for it never was obfcrvcd, but either when 

 the engine, after working ftowly, was made to work quicker, 

 or, after having been flopped for a few minutes, was fet to 

 work again. 



I conlidered the vapour which wc hud difcovered in the 

 vault to arife from the moifture of the fide of the rock next 

 the furnace, which being expelled by the great heat of the 

 furnace, and converted into vapour, uas able to force its way 

 through the pores of the rock into the vault; but that being 

 in a manner confined within the rock, by the preflure of the 

 condenfcd air, it found ilfclf at liberty to come into the vault 

 only when the condenfation abated confiderably, or was to- 

 tally removed by the going flow, or flopping of the engine. 

 It alfo occurred-to me, that the air, in a flate of condenfa- 

 tion, might poffibly be capable of holding a greater quantity 

 of water in folution, which might precipitate fuddenly into 

 vapour or mift when the condenfation abated. I imagined, 

 therefore, that the very fmall quantities of water we at times 

 difcovered, proceeded from nothing elfe but this vapour in its 

 paflage to the furnace along with the blaft, being condenfed 

 into water, by the coolnefs of the educlion-pipe and iron 

 wind-cheft. The quantity of water did not appear to amount 

 to a gallon in twenty-four hours. 



A few days after I had made this experiment, the water 

 ccafed entirely to make its appearance, either at the tweer or 

 at the hole in the wind-cheft j but the furnace did not come 



into 



