176
Class 1.—MINING AND MINERAL PRODUCTS.South Side—Abeas S. 1 to S. 27.
[United
(c) The same, after a second crystallization.
(//) Rich lead, containing 81 oz. 1 dwt. 8 grains ofsilver; and now ready for the last process of oxidization,by which the silver is finally separated from the lead.
(e) Marketable lead from the crystallizing process; andwhich contains from A to f of an ounce of silver per ton.
(/) Models of the great ingot moulds employed forforming the pigs of lead of commerce.
( g ) Model of the great spoon-strainers employed forseparating the pure, or nearly pure lead, from the moltenliquid.
The operation depends upon the property which leadpossesses in weak alloys of crystallizing at a certain tem-perature, by which means those crystals, at the momentof forming, can be extracted, and thus separated fromthe silver mass.
By a particular manipulation in transferring the con-centrated lead and silver from pot to pot, the mass is atlast reduced to an alloy, containing some 80 or 90 ouncesof silver to the ton of lead, and much beyond whichpoint it is not found advantageous to crystallize.
The rich lead is now simply melted in the refining fur-nace, on a very large cupel, formed of bone ash, exposinga great surface to the draught of air passing over it.The oxygen of the atmosphere is rapidly imbibed by thelead, which becomes the litharge of commerce. This israked off as quickly as it forms; and finally, the silver isleft perfectly, or very nearly, pure, and run into ingotsfor the market.
('/) Is the litharge or minium thus withdrawn fromthe melted surface.
Model of the lead vapour-condensing apparatus, atWanloch Lead-mines, as improved by the exhibitor.
A collection of minerals from the Wanloch Lead-mines,or Lead-hills.
[In all great smelting works of this class, the smokerising from the furnaces is highly charged with noxiousvapours, containing, besides other poisonous matter, alarge quantity of lead ; many attempts have been madeto obviate this nuisance, and the system adopted by theexhibitor has been found to be very successful.
An oblong building in solid masonry, about 30 feet inheight, is divided by a partition wall, into two chambers,having a tall chimney or tower adjoining, which commu-nicates with one of the chambers at the bottom. (Seeengraving.) The smoke from the various furnaces, eightin number, and about 100 yards distance from the con-denser, is carried by separate flues into a large chamber;from thence, by a larger flue, it enters the first chamberof the condenser at the very bottom, and is forced up-wards in a zigzag course towards the top, passing fourtimes through a shower of water constantly percolatingfrom a pierced reservoir at the summit of the tower.The smoke is again compelled to filter a fifth time, througha cube of coke some two feet square, through which astream of water filters downwards, and which is confinedto its proper limits by a vertical grating of wood.
The smoke having reached the top, is now opposite thepassage, into the second, or vacuum chamber. This istermed the exhausting chamber, and is about five feetby seven feet inside, and 30 or more feet in height. Onits summit is fixed a large reservoir, supplied by an am-ple stream of water, always maintaining a depth of 6 to10 inches. The bottom of this tank is of iron, having se-‘veral openings, or slots, 12 in number, about an inch inwidth, and extending across the whole area of the reser-voir, communicating directly with the chamber beneath.On this iron plate, works a hydraulic slide-plate,, withopenings corresponding in one position with those in thereservoir. This plate receives a horizontal reciprocatingmotion from a water-wheel or other power, driven bymeans of a connecting-rod and crank.
In the middle of every stroke, the openings in theplate correspond with those in the bottom of the re-servoir, and a powerful body of water falls as a showerbath, the whole height of the vacuum chamber, and indoing so, sweeps the entire inside area, carrying with itevery particle of insoluble matter held suspended in thevapours coming from the furnaces.
The atmospheric pressure, of course, acts in alternatestrokes as a blast at the furnace-mouths, and causes adraught sufficiently strong to force the impure vapours,through the various channels, in connexion with thewater, the wet coke and exhausting chamber, until itpasses purified and inert into the atmosphere.
The water, saturated with particles of lead, &c., heldin mechanical solution, finally passes into great dykes orreservoirs, excavated for the purpose; and there depositsits rich charge of metal.
(h) Is the lead collected from this “fume,” or deposit,which contains about 33 per cent, of pure lead, and about4 oz. 17 dwts. and 7 grains of silver to the ton.
(*) The condensed fume roasted.
The results of this arrangement are most apparent, andbeneficial to the surrounding neighbourhood. Formerly,the noxious fumes passing from the shafts of the furnaces,poisoned the neighbourhood ; the heather was burnt up,vegetation destroyed, and no animal could graze, or birdfeed near the spot. Now, the heather is seen in luxu-riance close around the establishment, the sheep grazewithin a stone’s throw of the chimney’s base, and gameon all sides take shelter.—J. A. L.]
510 Wallace, William, & Cowper, T., Nenthead,Alston —Proprietors.
Carbonate of lead, from Little Eggleshope Lead Mine,in Teesdale, county of Durham.
Minerals from Alston.
511 Barrett, Captain—Producer.
Cobalt and copper ores from Conniston mines, nearKendal, Lancashire.
512 Blee, R., Redruth —Producer.
Cobalt ores, from Cornwall.
513 Liskeard Committee —Producers.
Various specimens, including iron pyrites; hornblende,
and antimony. __
514 Muschamp, William, Derwent Lodge, Sunderland —
Producer.
Specimen of Cally copper ore, a portion of a largeblock weighing 6 cwt., recently raised at the Cally mines,near Gatehouse of Fleet, Kirkcudbrightshire, Scotland .The rock in which it is found, is brown killas, or clayslate. The lode is from 2 feet 6 inches to 4 feet wide,and is composed of sulphate of barytes, gossan, and othermineral soils. The ore generally lies in solid ribs orbunches, and is mostly unmixed with any matrix or veinstuff. In some places it has been found 4 feet wide. Theore is of very rich quality, being a compound of thegreen and blue carbonates of copper, black, grey, andyellow copper, yielding from 25 to 30 per cent, of metalliccopper. It has been sold in the market from 201. to 25 1.per ton. _
515 Dublin Society —Producer.
Copper ore, from Knockmahon mines, Waterford.