II. Account of certain Phenomena obferved in the Air Vault 

 of the Furnaces of the Devon Iron Works* ; together 

 with fome praclical Remarks on the Management of 

 Blast Furnaces. By Mr Roebuck, in a Letter to Sir 

 James Hall, Bart. Communicated by Sir JAMES Hall. 



[Read, July 2. 1798.] 



SIR, 



IHave examined my memorandums, concerning the obfer- 

 vations I made on the condenfed air in the air vault of the 

 Devon Iron Works, near Alloa ; and, according to your requeft, 

 I now tranfmit you an account of them ; and alfo of an expe- 

 riment I made, when a partner and manager of thefe works, in 

 order to increafe the produce of blafl furnaces. 



The two blafl furnaces at Devon are of large dimenfions, 

 each being 44 feet high, and about 1 3 feet wide in the bofhes, 

 or widefl part, and are formed on a fteep bank, by two pits 

 funk in a very folid ftratum of coarfe grained freeflone. 



These pits were afterwards fhaped and lined in the ufual 

 manner of blafl furnaces, with common bricks and fire bricks, 

 and the hearth was laid with large blocks of the flone that had 

 been dug out, and which ferve the purpofe of fire ftones. At 

 the back of the two furnaces, next the bank, the air vault is ex- 

 cavated 



* These iron works are on the banks of the river Devon, which runs into the 

 Frith of Forth near Alloa. They are 3 miles from Alloa, and 8 from Stirling. 



