a term which is used in Britain to signify the saline substance obtained by burning sea-weed, which is chiefly employed in the manufacture of green-glass. Different species of sea-weed, belonging to the genus fucus, and order algae, are cultivated for this purpose. These plants are thrown on the rocks and shores in great abundance, and in the summer months are raked together and dried as hay in the sun and wind, and afterward burnt to the ashes called kelp. The process of making it is thus: The rocks, which are dry at low water, are the beds of great quantities of sea-weed; which is cut, carried to the beach, and dried: a hollow is dug in the ground three or four feet wide; round its margin are laid a row of stones, on which the sea-weed is placed, and set on fire within, and quantities of this fuel being continually heaped upon the circle, there is in the centre a perpetual flame, from which a liquid like melted metal drops into the hollow beneath; when it is full, as it commonly is ere the close of day, all heterogeneous matter being removed, the kelp is wrought with iron rakes, and brought to an uniform consistence in a state of fusion. When cool, it consolidates into a heavy dark-coloured alkaline substance, which undergoes in the glass-houses a second vitrification, and when pure affumes a perfect transparency. See Soda, Chemistry Index.