FUENACE 



517 



1007 



ammoniac (chloride of ammonium) to the water. The addition of a small proportion 

 of glycerine has also been recommended. 



FURNACE. The construction of furnaces for the more important metallurgical 

 operations will be found under the heads of the different metals, for the separation 

 of which from their ores they have been employed. All the arrangements of the 

 BLAST FURNACE, PUDDLING FURNACE, and REHEATING FURNACE, will be found under 

 IRON. Under the heads of COPPER, TIN, LEAD, SILTED, ZINC, &c., will be described 

 the furnaces used in the production of those metals. 



In like manner, the several kinds of furnaces employed in GLASS and other manu- 

 factures requiring the application of heat, are described in their respective places. 



There remains, therefore, only one or two very ingenious forms of furnace, by which 

 great heat can be obtained, for any purpose, to be mentioned in this place. 



Furnace of Assay. Under ASSAY a furnace constructed by Messrs. Anfrye and 

 D'Arcet is mentioned, which gives some 

 peculiar facilities and economy to the 

 process by fire. 



It had originally a small pair of bellows 

 attached to it, for raising the heat rapidly 

 to the proper vitrifying pitch. This is 

 not shown in the previous figure. 



The furnace is 17s inches high and 7| 

 inches wide, made of pottery or fine clay, 

 as represented in Jig. 1007, supported on 

 a table having a pair of bellows beneath 

 it. The laboratory is at b, the blow-pipe 

 of the bellows at d, with a stopcock, and 

 the dome is surmounted by a chimney a c, 

 in whose lower part there is an opening 

 with a sliding door for the introduction 

 of charcoal fuel. The furnace is formed 

 in three pieces : a dome, a body, and an 

 ash pit. A pair of tongs, a stoking hook, 

 a cupel, are seen on the right hand ; and 

 the plan of the stoneware grate pierced 

 with conical holes and a poker are seen 

 to the left. 



Gas Furnaces. G-as has been em- 

 ployed, of late, with much advantage for 

 heating crucibles, and many forms of 

 burners have been introduced for the pur- 

 pose of producing such jets as will yield 

 the proper quantity of gas, and unite it 

 with the right proportion of air, for pro- 

 ducing the most intense heat ; which can 

 be applied in a convenient manner. The 

 power of the burner, of whatever kind it 

 may bo, must be increased by surrounding 

 the flame with a jacket of fire clay or 

 some non-conducting substance, which 

 will prevent the dissipation of heat by 

 radiation. By attending to this a very 

 high temperature may be produced with 

 but a small expenditure of gas. 



Griffin's Blast Gas-Furnace. This is a more powerful apparatus, adapted for 

 metallurgic operations, such as fusing considerable masses of metal, assaying, roasting, 

 &c. It consists of two parts : first, of a particular form of gas-burner, which is 

 supplied with gas at the usual pressure, and with a blast of common air, supplied by 

 bellows or a blowing machine at about ten times the pressure at which the gas is 

 supplied ; and secondly, of a furnace, which is built up in a particular manner, round 

 the flame produced by the gas-burner and the crucible exposed to ignition. The 

 object of this particular construction is to accumulate and concentrate in a focus the 

 heat produced by the gas flame, and to make it expend its entire power upon any 

 object placed in that focus. 



This apparatus can be made of various sizes, according to the amount of "work 

 required from it. 



The gas-burner is a cylindrical iron reservoir shown in section in fig. 1008, which is 

 drawn on a scale of one-third the full size. It contains two chambers, not in com- 



