Portable furnaceJ 275 



with ftoppers made of crucible ware. The lower opening c, Defcriptlori of 

 Is thea(h-pit of the furnace ; it, is compofed of two regifler t^J^ntht^ll 

 plates. Aiding backwards and forwards in grooves, in order operation, 

 to diminilh, or enlarge the opening for regulating the heat, 

 by admitting or excluding air at pleafure. In the fide of the 

 furnace a hole is Cut, furnifhed with a ftopper and door, for 

 paffing a tube through the fire-place of the furnace ; an expe- 

 dient very neceffary for a variety of themical proceffes, 

 fuch as exhibiting the decompofition of Water, alcohol^ 

 oils, &c. for the preparation of phofphiiret of lime, for 

 paffing gafes over ignited bodies, &c. In either of the 

 openings in front of the furnace, a muffle may be placed for 

 performing the procefs of cupellation of gold, lilver. Sec* 

 or, the neck of a retort (placed on a ftand in the body of the 

 furnace) may be paffed through it, for diftillation by the 

 naked fire ; for procuring gafes which require a high degree 

 of heat, &c. If the iron fand-pot h be removed, and a 

 circular plate properly lined with fire-clay be placed in its 

 room, the furnace becomes converted into a, wind-furnace * 

 the fuel is then to be introduced through either of the open- 

 ings in front. The iron plate at the top has a hole in the 

 centre, furniflied with a ftopper> to enable the operator to 

 infped his procefs at pleafure. If the iron-pot be placed 

 inverted on the opening of the furnace^ it forms a dome, and 

 it then becomes a reverberating furnace. The iron-pot 

 when filled with fand, or water, placed in its proper litua-^ 

 tion, ferves as a; fand or water-bath> for the proceffes of dif- ^ 

 tillation by means of glafs retorts, for evaporations, fubli- 

 mations, digeftions, &c. Coake and charcoal are the befi: 

 fuel, this mixture burns without fmoke, and gives a ftrong 

 uniform and permanent heat; charcoal and common cOal; 

 or coal only, does likewife very well. The elbow of the 

 chimney a may be direded into that of the fire-place of any 

 apartment. 



The furnace is furnifhed with caftors, and may therefore 

 be eafily moved, according to the convenience of the ope- 

 rator. I am> S I R, 



YouT moft obedient fervant, 



FREDERICK ACGUM. 



Old Campion 'Street, Soho, 

 Nov, 21, 1803. 



T 2 XV. Obfavdtiond 



