ELASTICITY OF FLUIDS is accounted for from their particles being all endowed with a centrifugal force; when Sir Isaac Newton (prop. xxxii. lib. 2.) demonstrates, that particles, which naturally avoid or fly off from one another by such forces as are reciprocally proportioned to the distances of their centre, will compose an elastic fluid, whose density shall be proportional to its compression; and vice versa, if any fluid be composed of particles that fly off and avoid one another, and hath its density proportional to its compression, then the centrifugal forces of those particles will be reciprocally as the distances of their centres.

ELASTICITY OF THE AIR is the force wherewith that element dilates itself, upon removing the force whereby it was before compressed. See AIR and ATMOSPHERE. The elasticity or spring of the air was first discovered by Galileo. Its existence is proved by this experiment of that philosopher-An extraordinary quantity of air being intruded by a syringe into a hollow glass or metal ball, till the ball, with this accession of air, weighs considerably more in the balance than it did before; upon opening the mouth thereof, the air rushes out, till the ball sink to its former weight. From hence we argue, that there is just as much air gone out, as compressed air had been crowded in. Air, therefore, returns to its former degree of expansion, upon removing the force that compressed or resisted its expansion; consequently it is endowed with an elastic force. It must be added, that, as the air is found to rush out in every situation or direction of the orifice, the elastic force acts every way, or in every direction. The doctrine of the elasticity of the air is a considerable branch of pneumatics. The cause of this elasticity has been commonly ascribed to a repulsion between its particles; but this can give us only a very slight idea of the nature of its elasticity. The term repulsion, like that of attraction, requires to be defined; and in all probability will be found in most cases to be the effect of the action of some other fluid. Thus, we find, that the elasticity of the atmosphere is very considerably affected by heat. Supposing a quantity of air heated to such a degree as is sufficient to raise Fahrenheit's thermometer to 212°, it will then occupy a considerable space. If it is cooled to such a degree as to sink the thermometer to 0°, it will shrink up into less than half its former bulk. The quantity of repulsive power, therefore, acquired by the air, while passing from one of these states to the other, is evidently owing to the heat added to or taken away from it. Nor have we any reason to suppose, that the quantity of elasticity, or repulsive power, it still possesses, is owing to any other thing than the fire contained in it. The VOL. VIII-PART 1.

supposing repulsion to be a primary cause, independent of all others, has given rise to many erroneous theories, and been one very great mean of embarrassing philosophers in their accounting for the phenomena of electricity.

ELATE, adj. & v.a. Lat. elatus, part. of verb ELA'TION, n. s. Jeffero, to exalt, &c., from e, forth, and fero, latum, to bring. Elevated; lofty; flushed with station or dignity. The verb seems to be derived from the adjective.

This king of kinges proud was and elat;
He wend that God that sit in majestee
Ne might him nat bereve of his estat.

Chaucer. Cant. Tales.
God began to punish this vain elation of mind by
withdrawing his favors.
Atterbury.
Oh, thoughtless mortals! ever blind to fate!
Too soon dejected, and too soon elate! Pope.
I, of mind elate, and scorning fear,
Thus with new taunts insult the monster's ear.
Id. Odyssey.

Or truth, divinely breaking on his mind,
Elates his being, and unfolds his power.

Thomson.

Fair was the blossom, soft the vernal sky: Elate with hope we deemed no tempest nigh: When lo! a whirlwind's instantaneous gust Left all its beauties withering in the dust.

Beattie.

ELATE, in botany, a genus of the monœcia order and triandria class: CAL. none: COR. tripetalous, with three stamina or with one pistil; FRUIT an oval acuminated plum. Species one only, an Indian tree.

ÉLATER, in zoology, a genus of insects, belonging to the order of coleoptera. The antennæ are setaceous; and an elastic spring or spine projects from the hinder extremity of the breast or under side of the thorax. By means of this kind of spring, the animal, when turned upon its back, contrives to leap up into the air, and so turn itself. It varies in size; and when the insect is young, and newly metamorphosed, its elytra are of a beautiful deep red; but in a few days they change to a much darker hue, and are nearly of a chestnut color. In the state of larvæ it inhabits the trunks of decayed trees, and is there transformed. With the help of its wings it issues from its prison, flutters upon flowers, wanders over the fields, and conceals itself in thickets or under the bark of trees.

ELATE'RIUM, n. s. Lat. An inspissated juice, light, of a friable texture and an acid and pungent taste. It is procured from the fruit o a wild cucumber. It is a very violent and rough purge.

ELATERIUM, EXarnotov, in botany, a genus of the monandria order, monoecia class of plants; natural order thirty-fourth, cucurbitaceæ, male or female: CAL. none: COR. salver shaped: CAPS.

B