Zinc Desilverization, 103 



had to be diseno-ao-ecl while it was at a white heat, before the 

 rich silver lead could be discharged from the furnace. The 

 percentage of breakage was thus greatly increased, so that between 

 the necessity of getting rid of the clinkers on the outside of the 

 retort, and the necessity of disengaging the neck every time it 

 was discharged, the number of retorts broken was very large. 

 The syphon proved to be a complete remedy, but was difficult to 

 use, much more so than the polling-pot syphons. The objection 

 to using these furnaces was not only the breakage of the retorts 

 but the large quantity of fuel they consumed. 'J'he Brodie fur- 

 nace, with two tiers of retorts, consumed less than the Chelten- 

 ham furnace, but the retorts were more difficult to manage. 

 The use of petroleum seemed to be a real progress, and the use 

 of gas was proposed, when the invention of the tilting-furnace 

 overcame all difficulties, and it is now almost universally used 

 for this purpose. 



The general shape of Faber du Faur's furnace is essentially 

 the same as that at Cheltenham ; but it is suspended on pivots, 

 so that it is capable of rotation by means of a worm attached ot 

 a hand- wheel, as in the American type of the furnace. Fig. 11, 

 or by means of a lever, as in the German type, used in Newark 

 and in Prussia, Fig 12. The furnace is 3 feet 3 inches by 

 2 feet 11 inches in section, by 3 feet high on the outside, 2 feet 1 

 inch by 2 feet 3 inches, and 2 feet 9 inches from the grate-bars 

 to the centre of the arch on the inside. There is an opening 

 11 inches in diameter on the top, for the introduction of the 

 fuel, and on the back a flue 6 feet 6 inches leading to the 

 chimney. There are 12 grate-bars 1 inch square and 2 feet 9 

 inches long set on edge. The retort is built into the furnace in 

 the same way as at Cheltenham. 



Fig. 13 gives the proposed plan of the furnaces at Salt Lake, 

 showing the disposition of the eight furnaces, a, with regard to 

 the main chimney, (/, and a section across the flue,/. At Mans- 

 field Valley, the chimney is at the end of the line of furnaces. 

 The weight of the iron for a furnace is nearly as follows : — 



