]192 



2163 



They were mounted with from 6 to 8 crucibles or pots (figs. 2163, 2164), arched over 

 with a cupola a, placed under a conical chimney b, which served to give a strong 

 draught, and to carry off the smoke. In this cone there were as many doors, c, c, c, 

 (is there were pots in the furnace ; and an equal number of vents d, d, d, in the 



cupola, through which the smoke might 

 escape, and the pots be set. In the 

 surrounding wall there were holes for 

 taking out the pots when they became 

 unserviceable ; after the pots were set, 

 these holes were bricked up. The pots 

 were heated to ignition in a reverbera- 

 tory furnace before being set, and were 

 put in by means of iron tongs supported 

 upon two wheels, as is the case with 

 glass-house pots. In figs. 2163, 2164, e, 

 is the grate ; /, the door for fuel ; g, the 

 ash-pit. The pots, h, h, h, have a hole 

 in the centre of their bottom, which is 

 closed with a wooden plug, when they 

 are set charged with calamine, mixed 

 with coal; which coal prevents the 

 mixture from falling through the orifice, 

 when the heat rises and consumes the 

 plug. The sole of the hearth i, i, upon 

 which the crucibles stand, is perforated 

 under each of them, so that they can be 

 reached from below ; to the bottom 

 orifice of the pots, when the distillation 





begins, a long sheet-iron pipe, k, is 

 joined, which dips at its end into a vessel, I, for receiving in drops the condensed 

 vapours of the zinc. The pot is charged from above, through an orifice in the lid, 

 which is left open after the firing until the bluish colour of the flames indicates the 

 volatilisation of the metal, immediately whereupon the whole is covered with a fire- 

 tile, m. The iron tubes are liable to become obstructed during the distillation, and 

 must therefore be occasionally cleared by means of an iron bar. When the operation 

 is terminated the pipes must be removed, and the carbonaceous and other residual 

 matters extracted from the pots. In this figure, 1, 2, is the level of the upper floor ; 

 3, 4, level of the lower ceiling of the lower floor. Fig. 2164 is a ground plan on 

 the level of 1, 2 ; only one half being here shown. J. A. P. 



The general consumption of Spelter throughout the world is about 67,000 tons per 

 annum ; of which about 44,000 tons are made to take the shape of rolled sheets, and 

 these are estimated to be applied as follows, each quantity being somewhat below the 

 truth : 



Roofing and architectural purposes 

 Ship-sheathing .... 

 Lining packing-cases . 

 Domestic utensils .... 



Ornaments 



Miscellaneous 



Tons. 



23,000 

 3,500 

 2.500 



12,000 

 1,500 

 1,500 



44,000 



Five-and-tweuty years ago the quantity used for roofing did not exceed 5,000 tons ; 

 none was employed for ship-sheathing or lining packing-cases ; and stamped ornaments 

 in zinc date only from 1852. 



From the low temperature at which zinc fuses, and from the sharpness of im- 

 pressions possessed by castings in this metal, it is much employed on the Continent for 

 the production of statues and statuettes. The uses of this metal in the preparation of 

 alloys has already been noticed under the head of ALLOTS. It is also employed liko 

 tin for coating iron, producing what is known as ' galvanised iron.' (See GALVANISED 

 IKON.) The disinfectant liquor of Sir W. Burnett is chloride of zinc, and the oxide 

 of this metal is much employed as a pigment in place of white lead. (See BUHNETT'S 

 FLUID, aud ZINC WHITE.) 



