270 GILDING. 



from a solution of blue vitriol. When the metal 

 to be gilt is thus covered over with a thin coat 

 of precipitated mercury, it readily receives the 

 amalgam. 



On the subject of gilding by amalgamation, Dr. 

 Lewis has the following remarks : " There are 

 two principal inconveniencies in this business ; 

 one, that the workmen are exposed to the fumes of 

 the mercury, and generally, sooner or later, have 

 their health greatly impaired by them : the other, 

 the loss of the mercury ; for though part of it is 

 said to be detained in the cavities made in the 

 chimneys for that purpose, yet the greatest part of 

 it is lost. From some trials I have made, it ap- 

 peared that both these inconveniencies, particu- 

 larly the first and most considerable one, might be 

 in a good measure avoided, by means of a furnace 

 of a due construction." 



If the communication of a furnace with its chim- 

 ney, instead of being over the fire, is made under 

 the grate, the ash-pit door, or other apertures be- 

 neath the grate, closed, and the mouth of the fur- 

 nace left open, the current of air, which otherwise 

 would have entered beneath, enters now at the top, 

 and passing down through the grate to the chim- 

 ney, carries with it completely both the vapour of 

 the fuel, and tlie fumes of such matters as are 

 placed upon it. The back part of the furnace 

 should be raised a little higher above the fire than 

 the fore part, and an iron plate laid over it, that 

 the air may enter only at the front where the 

 workman stands, who will be thus effectually se- 

 cured from the fumes, and from being incom- 

 moded by the heat, and at the same time have full 

 liberty of introducing, inspecting, and removing 

 the work. 



