285. ARCHELL, or PURPLE ROCK LICHEN (Lichen omphalodes), is a vegetable production, of somewhat crustaceous consistence, and leaf-like form; the segments with many lobes, and of dark purplish brown colour, with dull purple saucers.
This kind of lichen grows upon rocks on the high stony moors of several parts of England, Wales, and Scotland. When properly prepared, it imparts to woollen cloth a reddish brown colour, or a dull but durable crimson. If wool that has been dyed with it be dipped into a blue vat, it will acquire a beautiful purple tinge. It is sometimes used as a styptic; and was formerly applied as a remedy in inflammatory fevers and other complaints; but, in the latter respect, it is now entirely neglected.
286. ORCHALL, or DYER'S LICHEN (Lichen rocella), is a somewhat crustaceous and shrub-like vegetable production, of nearly cylindrical form, solid, without leaves, but little branched, and with blackish brown alternate tubercles.
In the Canary and Cape de Verd Islands, as well as in the Grecian Archipelago, orchall is found in great abundance. It likewise grows in Guernsey and in some parts of England, and is employed by dyers chiefly for giving a bloom to other colours. This is effected by passing the dyed cloth or silk through hot water slightly impregnated with it; but the bloom thus communicated soon decays after it has been exposed to the air. When prepared in a peculiar manner, orchall yields a rich purple tincture, fugitive indeed, but very beautiful. Mixed with a solution of tin it is said to dye a permanent scarlet. Orchall is the substance generally adopted for colouring the spirits of thermometers. And it is a remarkable circumstance that, as exposure to the air destroys its colour upon cloth, so the exclusion of the air produces, in a few years, a like effect upon the fluid in those tubes; but on breaking the tubes the colour is restored.
287. ICELAND LICHEN (Lichen islandicus) is a leafy, membranous, vegetable production, of brownish green colour, jagged at the edges, and fringed, having large and purplish brown saucers or shields.
The name of this lichen is derived from that of the island in which it chiefly grows. It is, however, also found in the Highlands of Scotland, and in some of the northern parts both of England and Wales.
It abounds with nutritious mucilage; and, after having been steeped in water to extract its bitter and laxative qualities, it is sometimes used as medicine in coughs and consumptions. One ounce of Iceland lichen, boiled in a pint of water, yields about seven ounces of mucilage. The inhabitants of Iceland prepare from it a kind of gruel, which they mix with milk. They also boil it in several waters, and then dry and make it into bread. In Germany a durable brown dye is made by means of it; and, under another mode of preparation, it imparts an excellent black tinge to white woollen yarn.
288. BLADDER FUCUS (Fucus vesiculosus) is a species of sea-weed, of flat shape, with a middle rib, the edges entire, forked, and sometimes tumid at the ends, and furnished with several air bladders imbedded in the substance of the plant.
By far the most important application of this, one of the commonest of all our marine plants, is for the making of kelp, which, in Scotland, affords employment to many industrious families. So lucrative and so highly esteemed is the bladder fucus, and some other plants nearly allied to it, that the natives of several parts of the Western Islands have rolled large masses of stone into the sea, with a view to promote and extend their growth.
For the preparation of kelp these plants are dried, by exposure for some time to the sun and air. They are then burnt by degrees in a kelp furnace, which is generally a round hole dug in the earth. When the furnace is nearly filled with the remains of the burnt sea-weeds, the whole is briskly agitated with a rake or hook, till it is compacted, or becomes of a shining glutinous consistence, in appearance not unlike melted iron. It is then allowed to cool, and is afterwards placed in storehouses for exportation. In this state it is an impure kind of carbonat of soda. In the Orkney Islands every consideration is sacrificed to the making of kelp, nearly 3,000 tons of which are annually sent to market and sold at Leith, Newcastle, and other places, at the rate of from seven to ten pounds per ton of twenty-one hundred weight.