FACTURE.] In a purely metallic state, lead produces no action on the human system except such as arises from its mechanical properties; but, as soon as it becomes oxidised, it can combine with the contents of the stomach, and pro duce different effects, according to the nature of the substances it meets with. Painters are exposed to a distressing disease from the use of white lead, called Painter's Colic. The lid or cover of cisterns should never be made of lead, as the vapour which condenses on it pos sesses all the solvent power of distilled water. It is also unsafe to use water which has flowed over leaden roofs, more particularly in towns, as the surface of the load is almost invariably coated with some soluble salt. No kind of adulteration or impregnation with lead, from accident or ignorance, is more common than that of wine or cyder. Even a single shot of lead left by accident in a bottle after cleaning has produced severe colic ; and the more extensive use of the salts of lead to fine wines, as it is termed, that is, to remove their acid taste and make them sweet, has occasioned most serious consequences.
In the year 1818 lead ore was raised from sixteen counties in England and Wales ; viz., Cornwall, Devon, Cumberland, Durham, Northumberland, Westmoreland, Derbyshire, Shropshire, Somerset, Yorkshire, Cardigan, Caernarvon, Caermarthen, Flint, Montgomery, and Merioneth. The quantity of ore raised in that year, and of lead smelted from the ore, in the United Kingdom, was as follows : Ore. Lead.
England 55,638 tons. 39,142 tons.
Wales 16,305 „ 11,122 „ Scotland 2,588 „ 1,736 „ Ireland 1,912 „ 1,188 „ Isle of Man 2,521 „ 1,665 „ 78,901 54,853 From this we learn that three tons of ore produce about two tons of metallic lead. The richest English mines are in Durham. The richest Welsh in Fliutshire.
The pig and sheet lead imported in the three years 1848, 1849, and 1850, were 3,789, 7,216, and 11,977 tons, respectively. The quantities exported in the same three years were 6,129, 170,27, and 22,083 tons, respec tively.