HYG
78
FI Y M
ployed in tlie construction of hygrometers ; with equal facilitythey imbibe or impart the humidity of the atmosphere, and shewwith the greatest exactness when the least alteration takes place.”For easier weighing the paper, take a piece of round tin or brassthe size of a crown-piece, through the centre of which drill a hole,and also three others round it at equal distances: then cut about100 papers; and after putting them under the tin or brass, drivethrough each hole a strong pin into a board, in order to roundthem to the shape of the plate: the papers must then be separatedand exposed to the air a few hours with that already weighed, andso many of them taken as are equal to the weight already speci-fied. This done, thread them together through these holes madeby the pins, putting between every paper on each thread a smallbead, to prevent the papers from touching each other, and alsothat the air may be more readily admitted. The top of the hy-grometer is covered with a card cut to the same size ; and which,by its stiffness, supports all the papers, and keeps them in propershape. Before the papers are threaded, the beads, silk, card,and a thin piece of brass about the size of a sixpence, which mustbe placed at the bottom, and through which the centre-stringpasses, must be weighed with the greatest exactness, to bringthem to a certain weight, suppose 50 grains; now the paper inits driest state being of equal weight, they will weigh together100 grains ; consequently what they weigh more at any time ismoisture. To obviate the difficulty of trying experiments withweights and scales, Mr. Coventry contrived a machine or scaleby which to determine at one view the humidity or dryness of theatmosphere. This, with its case, is represented by fig. 7, PlateXCV. The front and back of the case are glass; the sides finegauze, which excludes the dust, and admits the air; the case isabout 10 inches high, eight inches broad, and four inches deep.A, a brass-bracket in front, behind which, at about inches dis-tance, is another; these support the axis of the index E, also ofthe beam D, and another which supports the stem B, to whichthe ivory-scale of divisions C is fixed. G, a brass-scale suspendedin the usual manner to the end of a beam l), and weighing ex-actly 100 grains. This scale is an exact counterpoise to the pa-per I and the different apparatus. The manner of suspension is asfollows : the axis of the beam g, which is made of brass, insteadof hanging on pivots as in common scales, turns with two steel-edges k k, fixed hi the extremities of the brass-axis: these edgesare shaped like the edge of a knife, and act on two steel concaveedges l /, in order to render the friction as small as possible. Dis a fine scale-beam fixed at right angles witli the axis g. E, thesteel-index fixed to the under side of the same axis. F, a brasssliding weight: A is the axis that holds the stem B to which thescale of divisions C is fixed. AA, the brass-brackets which sup-port the whole by four screws, two of which are seen at i i, thatscrew the brackets to the top of the case. The axis of the scaleof divisions is hung ou pivots, one of which is seen at m, that,should the case not stand level, the stem B may always be in aperpendicular situation. The hygrometer, before use, should bethus adjusted : to the end of the beam where the hygrometer issuspended, hang a weight of 100 grains, which is equal to theweight of the scale ; then move the sliding weight F up or downthe index E, till one grain will cause the index to traverse neithermore nor less than the whole scale of divisions ; then add half agrain to the scale, in order to bring the index to 0; and the in-strument, after taking off the 100 grain-weight, and hanging on thepapers, is fit for use ; then put grain-weights in the scale till theindex is brought within compass of the scale of divisions. Ex-ample : II is three grains on the brass-scale, and the index pointsat 10 : consequently there is three grains and 10 hundredths of agrain of moisture in the papers. If four grain-weights are kept,viz. 1, 2, 4, and 5, they will make any number from 1 to 9, whichare as many as will be wanted. Sometimes the index will con-tinue traversing within the scale of divisions for many days with-out shifting the weights; but if otherwise, they must be changedas occasion may require. “One great advantage, (says Mr. Co-ventry,) of this hygrometer, above all others that have attractedmy notice, is that it acts from a certain datum, namely, the dryextreme ; from which all the variations towards moist are calcu-lated with certairsy : and if constructed with that precision re-presented by the drawing,! it will afford pleasure to the curious inbserving the almost perpetual alteration of the atmosphere, even
in the most settled weather. In winter it will be constantly tra-versing from about 8 A. M. till 4 or 5 P. M. towards dry ; andin summer, from about 4 A. M. till 6 or 7 P. M. when the wea-ther is hot and gloomy, the hygrometer discovers a very greatchange towards moisture ; and when clear and frosty, that it con-tains a much greater quantity of moisture than is generally ima?gined.”
IIYG BOMETRY, [ vyp®-and purffw,] the art or science ofmeasuring the moisture of the atmosphere. See Hyrgometer.
IiYGROSCOPE, [vyj®- and trxmcw, hygroscope, Fr.] an in-strument to shew the moisture and dryness of the air, and to mea-sure and estimate the quantity of either extreme. It is commonlyused in the same sense with hygrometer, but Woltius properlymakes a difference from the etymology of the words. The hy-groscope (he says) only shews the changes of humidity or drynessin the air, but the hygrometer measures them.
IIYLAS, in fabulous history, son ofTheodamus, and favouriteof Hercules.
IIYLOPATIIIANS, ancient Greek philosophers, who derivedall things from dead and stupid matter, in the way of qualities andforms, general and corruptible.
H YLOZOISTS, [‘vxn, matter, and £«>i, life,] a sect of atheistsamong the ancient Greek philosophers, who maintained that mat-ter had some natural perception, without animal sensation, or re-flection in itself considered ; but that this imperfect life occasionedthat organization, whence sensation and reflection afterwardsarose.
HYMEN, or HYMEN .EUS, in ancient mythology, the sonof Bacchus and Venus, and the god of marriage. He was invokedin epithalamiums, and other matrimonial ceremonies.
Hymen, ['Tpiv,] anatomy, is a thin membrane or skin,sometimes circular, of different breadths, more or less smooth, andsometimes semilunar, formed by the union of the internal mem-brane of the great canal with that on the inside of the ala.', resem-bling a piece of fine parchment.
IlYMENyEA, the Bastard Locust Tree ; a genus of thenogynia order, and decandria class of plants ; natural order Lomen-taceax Calyx five-parted ; petals five, almost equal ; style twist-ed inwards; legume filled with farinaceous pulp. There is onlyone species, 11. courbaril, locust-tree. The wild bees are fond ofbuilding their nests in this tree, which grows to a considerable sizein the West-Indies .
IIYM ENOPTERA, [from vpm, membrane, and ottcct, awing,] in the Limucan system of zoology, an order of insects, hav-ing four membranaceous wings ; the tails of the females are furnish-ed with stings, which in some are used for instilling poison, andin others for merely piercing the bark and leaves of trees, and thebodies of other animals, in which they deposit their eggs. Thewasp and the bee are insects of this order. It consists of the fol-lowing genera :
Ammophila Mutilla
Apis Solia
Chalcis Sirex
Chrysis Sphex
Cynips Teulhredo
Formica Thynnus
Ichneumon Tiphia
Leucopsis Vespa.
IIYMETHUS, or HYMETTUS , in ancient geography, *mountain of Attica near Athens , famous for its marble-quarries,and for its excellent honey.
HYMN, [Yfzv®',] a song of joy, full of the praises of God , dis-tinguished from Threna, which is mourning-song, full of lamenta-tion. St. Hilary, bishop of Poictiers, is said to have been thefirst that composed hymns to be sung in churches, and was follow-ed by St. Ambrose . In the Greek Liturgy there are four kindsof hymns; but the word is not taken in the sense of upraise of-fered in verse, but simply of a laud or praise.The angelic hymn, orGloria in excelsis, makes the first kind ; the trisagion, the second jthe Cherubic hymn, the third ; and the hymn of victory andtriumph, called raivixi®*, the last. The hymns of the ancients ge-nerally consisted of three sorts of stanzas; one of which, calledstrophe, was sung by the band as they walked from E. to W. ano-ther, called antistrophe, was performed as they returned fromto E. the third part, or epode, was snug before the altar. r J he