1826.] as carried on in German]/. 199 



that each charge can be let down through an opening communi- 

 cating with the interior of a furnace. The calcming furnaces 

 are reverberatory, and of small dimensions. 



Four of these calcining furnaces are arranged together ; that 

 is in two rows, with a common stack in the centre. They are 

 surrounded by a screen, which prevents any vapours that may 

 escape through the front door from finding their way into the 

 building. The space within the screen communicates with the 



flue. „ p 1 • 



The form and arrangement of a furnace for this purpose may 

 be modified according to circumstances and the nature of the 

 fuel to be employed. The charge of ore in the Freyberg fur- 

 naces will appear to those accustomed to the large reverberatory 

 furnaces of this country, which often contain from 60 to 70 cwt. 

 of ore, as exceedingly small. It is possible that the Saxon fur- 

 nace may admit of being enlarged with advantage, or perhaps 

 improved in form ; but it should be borne in mind, that the 

 operation to be performed in it, is not a sioiple calcination of 

 ore, preparatory to its being brought into fusion, but a process 

 in which certain chemical changes and combinations are to be 

 effected, on which the success of the whole amalgamation 

 system depends ; and, therefore, to overcharge the furnace, or 

 to make it of such dimensions as might not be in every respect 

 most convenient and manageable, with a view to a trifling eco- 

 nomy of fuel, would be highly improper. 



On the part of the workmen, the utmost attention is required 

 to prevent the ore from caking together, which, from the mois- 

 ture contained in the salt, it is disposed to do ; especially it is 

 necessary to avoid the slightest degree of vitrification. The 

 charge should be kept well rabbled, and should be occasionally 

 shifted from one part of the furnace to the other, that the whole 

 may be equally exposed. The heat should also be regulated 

 according to the state of the ore. In the beginning, it should 

 be very moderate, and should be gradually increased as the pro- 

 cess advances. At Freyberg, when the ore becomes thoroughly 

 heated, the sulphur begins to burn ; and when this is perceived 

 to be the case, the fire in the grate is slackened ; and instead of 

 wood, which is the fuel employed in the first part of the process, 

 a small quantity of coal is thrown on, just to keep the fire alive. 

 The burning of the sulphur generally continues from two to 

 three hours ; and after it has ceased, the fire is increased, and 

 a tolerably strong heat is kept up for about another hour, until 

 on repeated trials on small quantities of ore, taken out with a 

 ladle from different parts of the furnace, no more sulphurous 

 smell can be perceived ; but rather a smell of muriatic acid, 

 denoting the decomposition of the salt. The ore is then drawn 

 out through the front door of the furnace, into a sort of iron 



