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An apartment of considerable extent is illumina- and universal drinks the northern part of Europe ted by it in the most fplendid manner, and the affords, as well as one of the most ancient. Mori. light reflected is extremely vivid and pure. It-In fevers the aliments prescribed by Hippocrates has no tendency to spoil the appearance of the were ptisans and cream of barley, bydromel, that apartment, or expose it to danger, as it never is, honey and water, when there was no tendency emits any sparks. Though in proceeding along to a delirium, Arbuthnot. the tubes it is cool, yet it contracts a proper de (2.) HYDROMEL is honey diluted in nearly an gree of heat in mixing with the atmospheric air. equal weight of water. When this liquor has not The colours of the illumination are beautiful and fermented, it is called simple hydromel ; and when variegated, but lose their brightness on being exe it has undergone the spirituous fermentation, it is posed to external air, and then assume a fainter called the vinous hydromel, or mead. Mead is an and less friking appearance. In bringing the hy: agreeable kind of wine: nevertheless it retains long drogene gas into contact with the atmospheric a taste of honey, which is unpleasing to some perair, Citizen Le Bon has provided either for aug. fons; but this taste it is faid to lose entirely by bementing or moderating its activity. This discovery ing kept a very long time. See Mead, No 2. may be turned to various purposes of convenience (1.) HYDROMETER. n. f (udwp and purpov.) and economy. It is calculated to extend to an An inftrument to measure the extent or profundió inconceivable degree the properties and powers ty of water. of light, and to employ in the most important (2.) The HYDROMETER is used to measure the uses those substances which pass off under the gravity, density, velocity, force, &c. of water and the form of smoke, without accomplishing any other fluids. See HYDROSTATICS, and Plate object of utility.The engine is called a THER. CLXXXV. fig. 1. Though it is incapable of deMOĻAMPE.

termining the specifie gravity of liquors with * HYDROGRAPHER. 1.f[idup and ypapas; perfect accuracy, yet in the way of public busihydrographe, Fr.] One who draws maps of the pess it has undoubtedly the advantage of epery fea. It may be drawn from the writings of our other, on account of the ease and expedition hydrographer. Boyle.

with which it can be used; and for this reafon it HYDROGRAPHIC, or 2 adj. a term applied bas been adopted by government, in order to deHYDROGRAPHICAL, I to CHARTS or Maps termine the Arength of spirituous liquors. Dr of sea-coafts, more usually called SEA CHARTS. Blagden, who was lately employed to make exSee CHART, No JIL. 1-4; and GEOGRAPHY, periments on this subject, is of opinion, that Se&. IX.

glass is the most proper material for the construc(1.) HYDROGRAPY. n. (vawe, and yopw;] tion of an hydrometer. (See Philof: Trans. vol. Description of the watery part of the terraqueous lxxx. p. 342.) Its fenfibility depends on the size globe.

of its stem. In the old areometers the ftem was (2.) HYDROGRAPHY is the art of meafuring and made fo large, that the volume of water dirdescribing the fea, rivers, canals, lakes, &c. placed between its leaft and greatest immersions With regard to the sea, it gives an account of its was equal to the whole difference of specific gratides, counter tides, soundings, baye, gulphs, vity between water and alcohol, or perhaps more; creeks, &c.; also of the rocks, shelves, fandswhence its scale of divisions must be very small, and Alrallows, promontories, harbours ; the distance could not give the specific gravity with much accuand bearing of one port from another ; with every racy. On this account weights were introduced, thing that is remarkable, whether out at sea or on by means of which the stem could be made smaller ; the coast.

each weight affording a new commencement of its HYDROLEA, in botany, a genus of the digy- scale; so that the fize of the divisions on a given Ria order, belonging to the pentandria class of length was doubled, tripled, &c, as one or more

and in the natural method ranking with weights were employed, the diameter of the ftem those of which the order is doubtful. The calyx being lefsened in the fubduplicate proportion of is pentaphyllous ; the corolla rotaceous; the bla. the increased length of the divisions. This mements at the base are cordate; the capsule is bilow thod, however, in our author's opinion, has been cular and bivalved.

carried to excefs; and the following is recomHYDROLOGY, 1. F. [from iowę, water, and mended as a proper mean betwixt these extremes aayos, a discourse.] a science which investigates to determine the specific gravity of spirituous liand explains the nature and properties of water; quors to three places of decimals. In this method comprehending Hydrostatics and Hydraulics. See the weight of water is supposed to be unity, or HYDROSTATICS.

with any number of cyphers annexed: “the whole (7.) * HYDROMANCY. n.f. [uswe and partie; compass of numbers, therefore, from re&ified fpihydromantie, Fr.) Prediaion by water.-Divina- rit to water, at 60° of heat, would be the differ. tion was invented by the Persians : there are four ence between 825, the weight of rectified [pikinds of divination; bydromancy, pyromancy, ae. rit, and soco the weight of water, which is 175. romancy, and geomancy. Ayliffe's Parergon. : To make allowance for the lightek' spirit and

(3.) HYDROMANCY. See DIVINATION,N°11.02. heaviest water, however, at all the common tem. HYDROMANTIC, adj. belonging to HYDRO- peratures, the difference may be supposed 220. MANCY,

The fem might show every 20 of these divifions, 6.) HYDROMEL. Th. f. [Edwp and plas; bedco and thus ten weights would be sufficient for the mel, Fr.) Honey and water. --Hydromel is a drink whole. Hence the inconvenience of shifting the prepared of honey, being one of the moft pleafant weights, which has always been complained of, Vol. XI. PART II.



plants ;

would in a great measure be avoided : as people veral lower countries. This he makes to be ore versant in that business would seldom err so far as of the great uses of mountains in the economy of to the whole amount of the difference previous to the universe. making any trial. Hence alfo the ftem may be · HYDROPHYLAX, in botany, a genus of the made small enough, and the scale graduated fo monogynia order, belonging to the tetrandria clase nicely as to make the instrument sufficiently accu• of plants. The calyx is tetrapartite ; the corolla rate.' According to this arrangement, it would funnel-shaped; the fruittwo-edged and one-feeded. be proper to have the weights adapted to the hy. HYDROPHYLUM, WATER LEAF: a genus drometer marked with the different specific gravic of the monogynia order, belonging to the pentanties which they are intended to indicate ; zero dria class of plants; and in the natural method on the top of the stem without a weight being ranking with those of which the order is doubtful. supposed to mean 800, and 20 at the bottom to The corolla is campanulated, with five melliferous fignify 820, which number the first weight would longitudinal Atria on the inside; the ftigma is bifid; carry; the succeslive weights being marked, 840, the capsule globofe and bivalved. There is only 860, &c.; and the division on the stem cut by the one species, viz. fluid under trial, would be a number always to be HYDROPHYLLUM VIRGINIANUM, the water added to that on the weight; the sum of the two leaf of Morinus. It grows naturally in Canada showing the true specific gravity. The weights and many other parts of America on moist spongy ihould undoubtedly be made to apply on the top ground. The root is composed of many strong of the item, so as never to come in contact with fethy fibres, from which arise many leaves with the liquor; and in using the hydrometer, its stem foot-Italks 5 or 6 inches long, jagged into three, fhould always be pressed down lower than the five, or seven lobes, almost to the midrib, inpoint at which it wili ultimately rest, that by being dented on their edges. The flowers are prowetted it may occasion no resistance to the fluid. duced in loose clusters hanging downwards, are The inftrument itself should be of as regular a bell-Ihaped, and of a dirty white colour. It may shape and with as few inequalities as poflible, that be propagated by parting the roots; which ougbt all impediments to its motions may be avoided. to be done in autumn, that the plants may be well

*HYDROMETRY.n.l. [üswe and morfov.] The rooted before fpring, otherwise they will require art of meafuring the extent of water.

a great deal of water. HYDROMPHALUS, in medicine and surgery, * HYDROPICAL. adj. LES PETIŁOS; by dropiçtik, a tumor in the navel arising from a collection of * HYDROPICK. S from hydrops, Latin.) 1. water.

Dropsical; difeafed with extravasated waterHYDROPHANES, OCULUS MUNDI, or LAPIS Cantharides heat the watery parts of the body, as MUTABILIS, a kind of precious stone highly urine, and hydropical water. Bacon's Nat. Hiftory. efteerned among the ancients, but little known to The world's whole sap is funk: the moderns till Mr Boyle made his observations The general balm the hydropick earth hath drunk. upon it. Its specific gravity is about 2'048 ; its

Donne. colour of an opaque whitish brown ; it is not fo. --Hydropical swellings, if they be pure, are. pelluluble in acids nor affected by alkalies, but is easily cid. Wiseman. cut and polished. Sometimes it gives fire with Hydropick wretches by degrees decay, steel, sometimes not. It is infusible per se; but Growing the more, the more they waste away; when urged by a blowpipe, changes to a brown By their own ruins they augmented lie, ich brittle fubitance. It is found in beds over the With thirst and heat amidst a deluge fry. Blackti. opals in Hungary, Silesia, and Saxony, and over-One fort of remedy he uses in dropfies, the wathe chalcedonies and agates in Iceland. These ter of the hydropicks. Arbuthnot. 2. Resembling ftones in general are either of a yellowith green, dropsy.-Some men's hydropick insatiableness learnmilky grey, or of a yellow like that of amber. ed to thirst the more, by how much more they The most remarkable property of this stone is, drank. King Charles. Every luft is a kind of hythat it becomes transparent by mere immersion in dropick diftemper, and the more we drink the more any aqucous fuid; but gradually resumes its' we shall thirst. Tillotson. opacity when dry. See LAPIS MUTABILIS. HYDROPS, in medicine, the DROPSY.

HYDROPHLOGE, a word used by Mr Wie : HYDROSCOPE, an instrument anciently used gleb, for one of the component parts of water. for the measuring of time. It was a kind of waSee his Gen. Syf. of Hopfon, p. 39. tor clock, consisting of a cylindrical tube, conical

(1.). * HYDROPHOBIA. x.lo (uspopoßia; hydro. at bottom: the cylinder was graduated, or markphobis, Fr.] Dread of water.- mong those difmaled out with divisions, to which the top of the wa. lymptoms that follow the bite of a mad dog, the ter becoming succeflively contiguous, as it trickled bydrophobia, or dread of water, is the most remark- out, the vertex of the cone pointed out the hour. able. Quincy.

** See HYDROSTATICS, Part II. Se&. XII. (2.) HYDROPHOBIA has likewise been sometimes * HYDROSTATICAL. adj. (odwp and satinn.] found to take place in violent inflammations of the Relating to hydroftaticks; taught by hydrostaticks. ftomach, and in hysteric fits. See MEDICINE, IndA human body forming in such a fluid, will de.

· HYDROPHYLACIA, a word used by Kircher ver be reconcileable to this bydrostatical law: and some others who have written in the same tys. there will be always something lighter beneath, tem, to express thiofe great reservoirs of water and something heavier above; because the bone, which he places in the Alps and other mountains the heaviest in specie, will be ever in the midtt. for the supply of rivers which run through the le. Bentley.


HYDROSTATICALLY. adv. [from hydro- pound weight, examined bydrostatically, doth alRatical.] According to hydrostaticks. -The weight ways cuniain an equal quantity of folid mass. of all bodies around the earth is ever proportional Bentley. to the quantity of their matter: for instance, a IÍYDROSTATIC BALANCE. See BALANCE, Ś s.

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face is always parallel to the horizon, or perfect.

level; that, in fyphons, or when tated by YDROSTATICKSn. S. (üswe, and stairn; H

the wind, it makes ifochrone vibrations, or unduhydrostatique, Fr.) The science of weigh. lations like a pendulum ; that it runs off where faing fluids; weighing bodies in fluids.

voured by the smallest defcent, &c. &c. Yet all This science not only treats of the weighing of these facts, being common and familiar, occafion fluids, and of folid bodies in them (as Dr John. no surprise to mankind in general. Son observes above), but comprehends their na. FLUIDITY is caused by a certain degree of fire, ture and properties in general, particularly their which, when employed for this purpose, disapprellure, gravity, equilibrium, and motions. pears with respect to any other sensible or percep-,

This last branch of the subject, when treat. tible effect. It does not dilate the volume, but ed of by itself, forms a distinct science, entitled resists the particular attachment of the parts. HYDRAULICS; but it is so necessarily connected Some have endeavoured to give mechanical ideas with the other branches of HYDROSTATICS, that of a fluid body, by comparing it to a heap of fand: it would be improper to separate them, farther but the impossibility of giving fluidity by any kind than by describing the former as the ift part, and of mechanical comminution, will appear by conthe latter as the 2d part of this treatise.

fidering two of the circumstances necessary to con

stitute a fluid body: 1. That the parts, notwithPART I. , HYDROSTATICS.

standing the greatest compression, may be moved, Sect. I. Of FLUIDITY.

'in relation to each other, with the smallest con

ceivable force, or will give no sensible resistance to By HYDROSTATICs, properly so called, in con. motion within the mass in any direction. 2. That tradifinction from HYDRAULICS, we are taught the parts shall gravitate to each other, whereby how to determine the gravity or pressure of fluids there is a constant tendency to arrange themselves upon solids, or upon each other, in vefsels where about a common centre, and form a spherical bowater is not allowed to escape or run off, but re- dy; which, as the parts do not refift motion, is mains at rest.

easily executed in small bodies. Hence the apSIR ISAAC NEWTON's definition of a fluid is pearance of drops always takes place when a fluid much the same with that of the late Mr George A. is in proper circumstances. dams, whose writingson this subject we shall chief Let us now fee how far these qualities may be ly quote in the present treatise. He defines a fluid procured by mechanical operations, even executed to be a body whose parts are so loosely connected without those imperfections that necessarily attend together, that they easily yield to any force im- human performance. A body of fand, the para pressed upon them, and move freely amongst each ticles of which should be perfectly spherical and other. In this sense, fire, air, &c. are confider- polished, or smooth, would only imitate a fluid ed as fluids. in alniot every physical speculation, in being able to spread itself upon a smooth plane where experiment can reach, the subject admits instead of lying in a heap, but would possess neiof some illustration; where that is denied, the ther of the two qualities essential to a fuid body. reasonings are in general vain and conjectural. For a heap of spherical bodies, if compressed, We do not know the form of the parts of which could not move by relation to each other, except fluids are composed, and can make no experi- by a force sufficient to balance that by which, in ments to reduce them into their primary particles. this case, they are necessarily retained in their pla

There is nothing more different in accuracy and ces. Neither can the parts of the supposed body truth, than that apprehension which is adequate of sand cohere, either to themselves or to other to the purposes of human life, and that which bodies, in the manner of fluids, as in each partiought to satisfy the investigation of a philofopher. cle the mass of gravitating matter must be great in Thus there is nothing more obvious to common proportion to the point of contact by which they observers than fluidity, yet the philosopher finds ihould cohere. If the cohefion of the particles of it a property difficult to be conceived, and which fand increased, the spreading quality would be he could not give credit to, if it was not render- diminished. ed familiar to him by custom and experience. It Many other differences might be pointed out; is a physical phenomenon which has not yet been but fuppofing every thing else favourable to the explained, and of which it is very difficult to give mechanical theory, yet still there would remain a clear account. It is, indeed, impossible to com to be explained the operation of fire, which is so prehend, how a material and incompressible sub. effential to fluidity. This would lead us too far, stance can be composed of parts fo elementary, to as it would render it necessary for us to investimoveable among themselves, and yet with fo lit. gate the nature of that resistance by which the fitle adherence, as to affume immediately the form gure of bodies is preferved in their hardness. By of any vessei into which it is poured; that its fur- fire hard bodies are made foft; but it is not pro

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