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8. White Lead . —This metallic oxyd is produced by exposingsheets of lead to the fumes of acetous acid ; and the principalmanufactory of it is .established at Portobello, near Edinburgh .It is used, when mixed with oil, for painting ships, houses, andarticles of wood and iron. Mills are employed for grinding thepaint, which are driven by men or horses; and, in one instance,at Glasgow ', by a steam power. Considerable quantities of whitelead are ground with chalk and oil, and exported to the WestIndies and America , for the purpose of painting. Red Lead,,or the red oxyd of lead, is also made in Scotland ; but the de-mand for it by painters is not considerable. It is used by whiteand brown potters, and also in the composition of flint glass,which it renders less difficult to cut or polish, and not so brittleas it would otherwise be. Muriate of Lead , or Patent Te/low, ismade at only one place in Scotland, near Edinburgh . It is acomposition of lead, and muriatic acid ; but is now very littleused.
9. Acetite of Lead . —This substance is known by the name ofSugar of Lead ; and it is made at four manufactories in Scot-land . At Rutherglen Bridge—the Cudbear work, near Glas-gow—Airdrie, in Lanarkshire—and Linlithgow , in West Lo-thian.
Alkalies. 1. Kelp _The most important alkaline produc-
tion of Scotland is Kelp, which is an impure soda, made in greatabundance from various kinds of marine plants. The plants arefound every where along the rocky shores of Scotland ; but inthe greatest profusion on the western coast, and the islands.They are cut., collected, dried, and burnt in rude kilns con-structed for the purpose, (sometimes in cast-iron kilns, which isan improved mode), and the alkali is formed in large masses.This is the kelp of commerce, and in this state it is sold in themarket. -
The quantity of kelp annually made in the Hebrides , for theseseveral years past, averages from 5000 to 5500 tons ; in Argyle-siiire about 350 ; in Caithness 140 ; and, on all the other shores,including those of the Orkneys , upwards of 4000, making a totalof about 10,000 tons., The number of people employed in thismanufacture, during the kelp season, is not less than ten thou-sand ; and, at many places, horses are used to carry the warefrom the shore to the kiln.
This article is extensively used by the soap and glass manu-factories ; and the price varies according to circumstances. Theexpense of making it is regulated by the price of labour, andthe difficulty of obtaining the plants. On the shores of the coun-ty of Inverness , for instance, it costs from 35s. to 50s. per ton;in the Hebrides , nearly 41. ; and in Ayrshire, from 4l. to 51. 10s.;nnd, on the whole, the average may be. estimated at about fourfounds Sterling.