WAV [354 3 WAV
Wlit«-JN"«. Salt, Sea-Coal, gfc while aboard Places thro' which the 0&m paffes in its whole Breadth,
Veffek in the Pool, or River are meafur'd with the Corn- the Wave is raifed ; then a Cavity » form d, which is again
Bufhe heap'd up ; or elfe five flriked Pecks are allow'd to fill'd up; which Change, while the Surface of the Water
fhe Bufhel.LThis'is called Water-Stetfure 5 .and exceeds undergoes its Particles go and re urn thro a fmall Space :
^XferMeafure by about three Gallons in the Bufhel. The Direction of this Motion is along CE and the Cele-
i. «» n . „ «=, r tv may be reprefented by that Line.— Let this Motion be
- »Jfe?£i2*£?«*j£.~* conceived to be P refolved into two other Motions, along G E
WATER-Toi/e. See Hydrometer.
Dr. Hook has contrived a Waterpoife, which may be of good fervice in examining the Purity, 8fe of Water. It confifls of a round glafs Ball, like a Bolt-head, about three Inches in Diameter, with a narrow Stem or Neck, {, of an Inch ; which being poifed with red Lead, fo as to make it but little heavier than pure fweet Water, and thus fitted to one end of a fine Balance, with a Counterpoife at the other ; upon the lead Addition of even ^-.-'h Part of Salt to a quantity of Water, half an Inch of the Neck will im- merge above the Water, more than did before. Thilofopb. Jranfall. N° 197.
WiTEE-&«fs, of the Saxon Waterfchap, denotes an Aqueduct. See Aqueduct.
WATER-.SW, a young Sprig, which fprings out of the Root or Stock of a Tree. See Shoot, Stock, £$g.
WATER-Jto, in the Sea Language, a fort of riding at Anchor ; when a Ship is moored neither crofs the Tide, nor right up and down ; but quartet'd betwixt both.
WATER-7«£fc, in Architecture, is a fort of Ledge, left in Stone or Brick Walls, about 18 or 20 Inches from the Ground : from which Place, the Thicknefs of the Wall be- gins to abate. See Wall.
Water-J^P)', in a Ship, is a fmall Ledge of Timber, ly- ing on the Deck, clofe by the Sides ; to keep the Water from running down there.
W ITHR-Wheel, an Engine for railing Water in great quantity out of a deep Well. See Persian Wheel.
WATERING, in Gardening, tgc. the Application of Wa- ter to the Soil of Plants, He. when not fufficiently moiften'd with Rain, Dew, i£c. See Soil, Vecetation, f£>c.
After fowing Seed of any kind, tho the Ground be ever fo dry, they mould never be water' d till they have been 4.8 Hours in the Ground ; and the Ground is a little fettled about 'em 5 otherwife, a too great glut of Nourifhment at firfl will be apr to burft 'cm. See Seed, and Sowing.
Care is to be taken, that the Leaves of young and tender Plants ben't water'd at all while the Weather is cold ; on- ly the Ground to be wet about 'em.
For hardy Plants and Seeds, if the Nights be cold, water in the Forenoon ; otherwife in the Evening.
Water that comes out of deep Pits, or Wells, fhould fland a Day in an open Veffel, ere it be applied to tender Plants in the Spring. Dung of Sheep, Pidgeons, or Hens, or Afhes, Lime, Site, infufed in the Water, will forward the Growth of Plants. See Manure.
Watering, in the Manufactures. — To Water a Sniff, is to give it a Luflre, by wetting it lightly, and then pafling it thro' the Prefs, or the Calendar, whether hot or cold. See Calendar, Tabby, Pressing, 2?c.
WATTLES, among Husbandmen, Grates or Hurdles, . or Folds for Sheep. See Park.
The Word is alfo ufed for the Gills of aCock : and the naked red Flefh that hangs under a Turkey's Neck.
WAVE, Unda, in Phyficks, tgc. a Cavity in the Surface of Water or other Fluid, with an Elevation afide thereof. See Fluid, and Water.
The Origin of Waves may be thus conceived. — The Sur- faceof a ftanding Water being naturally Plain, and parallel to the Horizon ; if by any means it be render'd hollow, as at A, (Tab. Hydrofiatics, Fig. 30.) its Cavity will be furround- ed with an Elevation BB ; this railed Water will defcend by its Graviry, and with the Celerity acquir'd in defend- ing, form a new Cavity ; by which Motions, the Water will afcend at the Sides of this Cavity, and fill the Cavity A, wtiile there is a new Elevation towards C ; and when this laft is deprefs'd, rhe Water rifes anew towards the fame Part. Thus arifes a fucceffive Motion in the Surface of the Wa- ter • and a Cavity, which carries an Elevation before it, is moved along from A towards C. This Cavity, with the Ele- vation next it, is called a Wave ; and the Space taken up by the Wave on the Surface of the Water, and meafur'd ac- cording to the Direction of the Wave's Motion, is called the Breadth qftbeWave. See River, and Undulation.
'the Motion of Waves, makes an Article in the New Phi- lofophy ; and rhe Laws thereof being now pretty well deter- min d, we fhall give the Reader the Subftance of what is taught thereon.
1°, Then, the Cavity, as A, is incompafs d every way with anElevation ; and the Motion abovemention'd expands it felf every way ; therefore the Waves are moved circu- larly.
2°, Suppofe, now, A B, (Fig. 31.) an Obftacle, againft which the Wave, whofe beginning is at C, ftrikes ; and we are to examine what Change the Wave fuffers in any Point, as E, when it is come to the Obftacle in that Point. In all
conceived to oe relolveo into two otner motions, along ( and D E, whofe Celerities are refpecf ively reprefented by thofe Lines. By the Motion along D E, the Particles do not act againft the Obftacle ; but after the Stroke, conti- nue their Motion in that Direction with the fame Celerity ; and this Motion is here reprefenred by E F, fuppofing E F and E D to be equal to one another : But by the Motion along GE, the Particles ftrike directly againft the Obftacle, and this Motion is deftroy'd ; for tho the Particles are elaf- tick 5 yet, as in the Motion of the Waves they run thro' but a fmall Space, going backward and forward, they proceed fo flowly, that the Figure of the Particles cannot be changed by the Blow ; and fo are fubject to the Laws of Percufllon of Bodies perfectly hard. See Percussion.
But there is a Reflexion of the Particles, from another Caufe : The Water which cannot go forward beyond the Obftacle, and is puffi'd on by that which follows it, gives way where there is the lcaft Refiftance ; that is, afcends : And this Elevation, which is gteater in fome than other Places, is caufed by the Motion along G E ; becaufe it is by that Motion alone that the Particles come againft the Obftacle. — The Water, by its Defcent, acquires rhe fame Velocity with which it was raifed ; and the Particles of Water are repell'd from rhe Obftacle, with the fame Force in the Direction E G, as that with which they ftruck
againft the Obftacle. From this Motion, and the Motion
abovemention'd along E F, arifes a Motion along E H, whofe Celetity is exprefs'd by the Line E H, which is equal to the Line C E ; and by the Reflection, the Celerity of the Wave is not changed ; but it returns along E H, in the fame manner, as if raking away the Obftacle, it had moved a- long E h.
If from the Point C, CD be drawn perpendicular to the Obftacle, and then produced, fo that D e fhall be equal to CD; the Line He continued, will go thorow c : And as this Demonfttation holds good in all Points of the Obftacle; it follows, that the reflected Wave has the fame Figure on that fide of the Obftacle, as it would have had beyond the Line A B, if it had not ftruck againft the Obftacle. — If the Obftacle be inclined to the Horizon, the Water rifes and defcends upon it, and fuffers a Friction, whereby the Reflec- tion of the Wave is difturb'd, and often wholly deftroy'd : And this is the Reafon why very often the Banks of Rivers do not reflect the Waves.
If there be a Hole, as I, in the Obftacle B L, the Part of the Wave which goes thto' the Hole, continues its Motion directly, and expands it felf towards Q_Qj and there is a new Wave formed, which moves in a Semicircle whofe Cen- tre is the Hole. For, the raifed Part of the Wave, which firft goes thro' the Hole, immediately flows down a little at the Sides ; and by defcending, makes a Cavity, which is furrounded with an Elevation on every Part beyond the Hole, which moves every way in the fame manner as was laid down in the Generation of the firft Wave.
In the fame manner, a Wave to which an Obftacle, as A O, is oppofed, continues to move between ON; but ex- pands it felf towards R, in a Part of a Circle, whofe Cen- tre is not very far from O. Hence we may eafily deduce,
what muft be the Motion of a Wave behind an Obftacle, as M N.
Waves are often produced by the Motion of a tremulous Body, which alfo expand themfelves circularly, tho the Bo- dy goes and returns in a right Line ; for the Water which is raifed by the Agitation, defcending, forms a Cavity, which is every where furrounded with a Rifing.
Different Waves do not difturb one another, when they
move according to different Directions. The Reafon is,
that whatever Figure the Surface of the Watet has acquir'd by the Motion of the Waves, there may in rhat be an Ele- vation and Depreflion ; as alfo fuch a Motion as is requir'd in the Motion of a Wave.
To determine the Celerity of the Waves, another Motion,
analogous to theirs muft be examin'd. Let there be
a Liquid in the recurve cylindric Tube EH, (Fig. 32.) and let the Liquid in the Leg EF, be higher than in the other Leg, by the Diftance I E ; which difference is to he divi- ded into two equal Parts at i. The Liquid by its Gravity defcends in the Leg E F, while it afcends equally in the Leg EH: fo that when the Surface of the Liquid is arrived at V, it is at the fame height in both Legs ; which is the only Pofition wherein the Liquid can be at reft : But by the Celerity acquir'd in defcending, it continues its Motion, and afcends higher in the Tube GH ; and in E F is deprefs'd quite to /, except fo much as it is hinder'd by the Friction againft the Sides of the Tube. The Liquid inthe Tube G H, which is higher, alfo defcends by its Gravity, and fo 1 the
