a, is the door of the fire-place; c, the perforated arches upon which the ore is piled in the chamber e, through the door d, and an orifice at top; the latter being closed during the distillation; f f are vents for conducting the mercurial vapours into two chambers i, separated by a triangular body of masonry m n; h is the smoke chimney of the fire-place; o o, are the ranges of aludels, in connection with the chamber i, which are laid slantingly towards the gutter q, upon the double inclined plane terrace, and terminate in the chamber h q; this being surmounted by two chimneys t. The mercury is collected in these aludels and in the basins at q and p, [fig. 661.] r is a thin stone partition set up between the two principal walls of each of the furnaces. v is the stair of the aludel terrace, leading to the platform which surmounts the furnace; z is a gutter for conducting away the rains which may fall upon the buildings.

Great apparatus of Idria.—Before entering into details of this laboratory, it will not be useless to recapitulate the metallurgic classification of the ores treated in it. 1. The ores in large blocks, fragments, or shivers, whose size varies from a cubic foot to that of a nut. 2. The smaller ores, from the size of a nut to that of grains of dust.

The first class of large ores comprises three subdivisions, namely; a, blocks of metalliferous rocks, which is the most abundant and the poorest species of ore, affording only one per cent. of mercury; b, the massive sulphuret of mercury, the richest and rarest ore, yielding 80 per cent. when it is picked; c, the fragments or splinters proceeding from the breaking and sorting, and which vary in value, from 1 to 40 per cent.

The second class of small ores comprises: d, the fragments or shivers extracted from the mine in the state of little pieces, affording from 10 to 12 per cent.; e, the kernels of ore, separated on the sieve, yielding 32 per cent.; f, the sands and paste called schlich, obtained in the treatment of the poorest ores, by means of the stamps and washing tables; 100 parts of this schlich give at least 8 of quicksilver.

The general aspect of the apparatus is indicated by [figs. 663], [664.] and [665.] [Fig. 665.] represents the exterior, but only one half, which is enough, as it resembles exactly the other, which is not shown. In these three figures the following objects may be distinguished; [figs. 663], [664.], a, door of the fire-place; b, the furnace in which beech-wood is burned mixed with a little fir-wood; c, door of the ash-pit, extended beneath; d, a space in which the ores are deposited upon the seven arches, 1. to 7., as indicated in [figs. 663.] and [666.]; e e, brick tunnels, by which the smoke of the fuel and the vapours of mercury pass, on the one side, into successive chambers f k.

[Fig. 664 enlarged] (89 kB)

f g h i j k l are passages which permit the circulation of the vapours from the furnace a b c d, to the chimneys l l. [Figs. 663.] and [664.] exhibit clearly the distribution of these openings on each side of the same furnace, and in each half of the apparatus, which is double, as [fig. 664.] shows; the spaces without letters being in every respect similar to the spaces mentioned below. [Fig. 664.] is double the scale of [fig. 663.]