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the subject, have been indicated; but to fix the ideas of the reader, with respect to the explanation, would, probably, be only to fix them in error.
LIGHTS, northern. See AURORA.
LIGHT HORSE, in military economy, English troops, mounted on swifter horses, and more lightly accoutred, than the life-guards, or heavy horse.
LIGHTER, in naval architecture, a large kind of boat, used in the river Thames for carrying heavy *goods, as coals and timber.
LIGHTNING, in meteorology, a flash of light suddenly appearing in the atmosphere, and commonly disappearing in the same instant; sometimes at * tended with clouds and thunder, and sometimes not.
Lightning is proved, by the experiments of Franklin, to be produced by the electric fluid. Thunder is the explosion of clouds charged with that fluid. Lightning is to thunder, what the flask is to the report of gunpowder.
A very remarkable property of lightning, the zigzag kind especially, when near, is its 'seeming omnipresence. If, when a clap of thunder, accompanied with this species of lightning, occurs, two
persovs are looking different ways, both will per. ceive the flash ; not only that indistinct illumina
tion of the atmosphere which is occasioned by fire 2. of any kind, but the form of the lightning itself;
and every angle it makes in its course, will be as distinctly seen by each, as if they had looked directly at the cloud whence it proceeded: and if : person were at that moment looking at a book, or any other object, that he held in his hand, he, also, would distinctly see the form of the lightning, between his eyes and the objects. This property seems peculiar to lightning.
The different forms of the Aashes of lightning are all equally found in electric sparks; so that an account of the origin of this difference of form may, by analogy, be drawn, Where the quantity of electricity is small, and, consequently, incapable of striking at any considerable distance, the spark appears straight, without any curvature, or angular appearance; but where the electricity is very strong, and, of consequence, capable of striking an object at a pretty considerable distance, it assumes a crooked or zig-zag form.
LIGNUM vitæ. The lignum vitæ tree is a native of the West Indies, and the warmer parts of America : there is also a species, a native of the Cape of Good Hope. It is a large tree, rising at its full growth to the height of forty feet, and measuring from fifteen to eighteen inches in diameter; having a hard, brittle, brownish bark, not very thick. The wood is firm, solid, ponderous, very resinous, of a blackish yellow colour, in the middle, and a hot aromatic taste. It is so hard as to break the tools which are employed in felling it; and is, therefore, seldom used as firewood, but is of great use to the sugar-planters for making wheels and eogs to the sugar-mills. It is also frequently wrought in bowls, mortars, and other utensils. It is imported into England, in large pieces of four or five hundred weight each, and from its hardness and beauty, is in great demand for various articles in the turnery ware, and for trucks of ship blocks. The wood, gum, bark, fruit, and even the flowers
of this plant, have been found to possess medicinal virtues.
LIMAX, the slug, of which there are sixteen speeies, the one which we shall notice is the Limax agrestes ; body whitish, with black feelers: five varieties, of which some have the power of secreting a large quantity of mucus from the under surface, and forming it into a thread like a spider's web; by this means it often suspends itself, and descends from the branches of trees, or any height it had crawled up to.
It is found in gardens, pastures, and groves, from May till December. One of the varieties of this species is that which has been recommended to be swallowed by consumptive persons; it is half an inch long, and when touched it sticks, as if dead, to the fingers.
(LIME, in ehemistry, an earth of a white colour, moderately hard, but easily reduced to powder.
** Lime and limestone differ very materially from each other. Limestone is tasteless, scarcely soluble in water, and without power to act on animal suh. stances; lime is the reverse of all this. Dr. Black has proved, that this difference is owing to the presence of a fixed air in limestone, and to the want of it in lime. This fixed air has received the denomination of carbonic acid gas. Lime, upon this foundation, is esteemed to be a simple substance; and limestone, a composition of carbonic acid and lime, with which is joined a quantity of water. Heat separates the carbonic acid from the lime.
LINEN, in commerce, a kind of cloth, made of flàxIn the linen-manufacture, one set of people are employed in ploughing and preparing the soil; sowing and covering the seed, weeding, pulliog, rippling, taking care of new seed, and watering and grassing the flax, till it is lodged at home: others in the drying, breaking, scrutebing, and heckling the flax, to fit it for the spinners; others in spinning and reeling it, to fit it for the weaver ; others in taking due care of the weaving, bleaching, beetling and finishing the cloth for the market,
LINNÆAN SYSTEM of vegetables. See Botany.
LINUM, LINT, or FLAX, in vatural history, a plant, from the fibres of which thread, and cloth, are manufactured.
The L. usitatissimum, or common annual flaxy is the species of linum cultivated for manufactures and medicine. Its stems are about two feet and a half bigh, garnished with narrow spear-shaped, alternate grey-coloured leaves, and divided, at their top, into peduncies, or foot-stalks, terminated by small
, blue, bell-shaped flowers, appearing in June and July, and succeeded by large round capsales, each containing one seed.
LIQUORICE, in the materia medica, the root of a plant, called by botanists “glycyrrhizza.
LIQUID : fluids have been divided into two classes, viz. those which are elastic, and the non-elastic, or those which do not sensibly diminish in bulk when subjected to pressure. The first class are airs or gases: the second liquids : hence we may define a liquid to be a fluid not sensibly elastic, the parts of which yield to the smallest pressure, and move on each other.
LIQUOR of fints. Alkalies have a powerful action on silica : they combine in different proportions : two or three parts of potash, with one of silica, give a compound, which is deliquiscept in the air,
and soluble in water : this was formerly distinguished by the name of liquor of flints, but it is now denominated silicated alkali.
LITURGY, a name given to those set forms of prayer which bave been generally used in the clirisrian church. The liturgy of the church of England was composed in the year 1547, since which time it has undergope several alterations, the last of which was in the year 1661.
Liver, in anatomy, a very large viscus, of a red colour, serving for the secretion of the bile or gall. Its figure is irregular; the upper surface being convex, smooth and equal; the lower, hollow and unequal. There is also a remarkable eminence called the porta, where the vena porta enters it.
LOADSTONE, the same with magnet, see MAG
-Loan, in finance, money borrowed by government for defraying the extraordinary expences of the state. See Stocks.
LOGARITHMS are artificial numbers, invented for the
purpose of facilitating certain tedious arithmetical operations.
If any series of numbers in arithmetical pro.' gression beginning with o, be taken, and a corresponding series of geometrical numbers beginning with 1, the former series will be logarithms to the corresponding numbers in the latter ; thus, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 logarithms. 1, 2, 4, 8, 16, 32, 64, 128, 256, 512 numbers.
Here 0, 1, 2, &c. are the logarithms of 1, 2, 4, &c. and it will be seen at once, 1. That “ Addition in logarithms answers to Multiplication in common numbers. puta