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GAG

GAETA, an ancient, aiul strong town of Naples, iu Lavoxo, 40■files of Naples.

G.ETC'LI, the- people of Gxtuiia, were, among the earliest in-habitants of Africa . They were distinguished by different epithets;as Nigri, Autolotes, Darx, ami Bauiurai. (Pliny .)

G.ETU.LIA, iu ancient geography, a country of Africa , ly-ing S. of Mauritania , divided into Ga-tulia Propria, and GxtuiiaVetus.

GAFF, a sort of boom or hole, frequently used in small ships, toextend the upper edge of the nii/.en; and always employed for thesame purpose on those sails, whose foremost edges are joined tothe mast bv hoops or lacings, and. which age usually extended bya boom below. Such are the main-sails of ajl sloops,, brigs, andSchooners.

GAGE, in our ancient customs, is only properly, used in speak-ing of moveables; for immoveables, Hypothecs is used. If thegitge perish, tire person who received it is not to answer for it, butonly for extreme negligence, &c.

Gage is also used for at challenge to combat. It was a pledge,which the accuser or challenger cast on the ground, and the othertook up as accepting the challenge ; being usually a glove, gaunt-let, cltaperoon, or the like.

Gage, among letter-founders, a piece of box, or other hardwood, variously notched: used to adjust the dimensions, slopes, & c.of the different sorts of letters.

Gage, in joinery, an instrument made to strike a line trulyparallel to the straight side of any hoard or piece of stuff". Tts chiefuse is for the gaging of tenons true, to tit into mortises; am) for gagingstuff" of an equal thickness. It is made of an oval piece of wood,titled upon a square stick, to slide tip and down stiffly thereon,and with a tooth, at the end of a staff", to score, to strike a line uponthe stuff" at any distance, according to the distance of the ovalfrom it.

Gage, in the sea-language. When one ship is to the windwardof another, she is said to have the weather-gage of her. They like-wise call the number of feet that a vessel sinks in the water theship’s gage; this they find by driving a nail into a pike near theend, and putting it down beside the rudder till the nail catch holdunder it; then as many feet as the pike is under water is called theslop’s gage.

Gage, Ahuko-mercurim., an apparatus contrived by Dr.Hale-, and applied in various forms to the branches of trees, to de-termine the force with which they imbibe moisture. In PlateLXXVIII. fig. 1, e, r, is a cylindric glass, c. g. of an inch diame-ter within, and eight inches long. Into this glass is introduced thebranch of a young thriving apple-tree, b, about three feet long,with lateral branches; the diameter of the transverse cut i beingthree-fourths of an inch. Having fitted the joint r to the tube at r,by folding a piece of sheep’s skin round the stem, it is cementedwith a mixture of bees-wax and turpentine melted together, in suchproportion as to make a very stiff" clammy paste when cold, andover the cement folds of wet bladders are bound firmly with pack-thread. To the lower end e of the large tube, a smaller tube z eis cemented, being about of an inch diameter, and 18 incheslong, and in substance full -j of an inch thick. These tubes are ce-mented together at e, with common hard brick-dust, or powderedchalk cement, and the joint is farther secured with the cement ofbees-wax and turpentine, over which a wet bladder is bound. Theapparatus being thus prepared, the branch is turned downwards,and the glass-tube upwards and then both tubes are lilled withwater; with the finger applied to tlte open end of the small tube,it is inverted and immersed in the glass-cistern x, full of mercuryand water. In this situation the lower end of the branch was im-mersed six inches in water, viz. from r to i ; the water was im-bibed by the branch at its transverse cut i ; and during its ascentinto the sap-vessels of the branch, the mercury rose in the tube czfrom the cistern t, so that in half an hour it was risen 5J incheshigh, as far as z. The height of the ntercurv indicated, in somemeasure, the force with which tire sap was imbibed, though not thewhole force ; because, while the water was imbibed by the branch,its transverse cut was covered with innumerable little hemispheresof air, and many air-bubbles issued out of the sap-vessels, whichparlK filled the"tube e r, as the water was drawn out qf it: andtherefore the height of the mercury could only be proportionableto tlte excess of the quantity of water drawn off, above the quanti-

ty of the air which issued out of the wood. If the quantity ot air issuing from the wood had been equal to the quantity of water iin"bibed, it is plain tiut the mercury could not rise at all, becausethere would be no room for it in the tube: but if 9 parts in 12of the water be imbibed by the branch, and only three such partsof air issue into the tube in the same time, the mercury must risenear six inches, and so proportionally in other eases. Dr. Halesobserved, that die mercury rose highest, in most cases, when thesun was clear and warm, and that it subsided three or tour inchestowards evening, but rose again the next day as it grew warm,though seldom so high as at first. He adapted the size and shapeof the glass apparatus to a great variety of branches of several sizes I:md of different kinds of trees, and repeated the experiment abovedescribed, mutatis mutandis, in a variety of instances. See hisVegetable Statics, vol. i. chap. ii. p. 84, Szc.

Gage, Bucket Sea, an instrument contrived by Dr. Hale, tofind the different degrees of coolness and saltness ot the sea, atdifferent depths. It consists of a common household pale or buck-et, wjtli two heads; which have each a round hole in the middle,about four inches in diameter, covered with square valves openingupward ; and that they may both open and shut together, there is asmall iron rod fixed to the upper part of the lower valve, and theother end to the lower side of the upper valve. So that as the buck-et descends with its sinking w eight into the sea, both the valvesmay open by the force of the water,, w Inch thus has a free passagethrough the bucket. But when the bucket is drawn up, then boththe valves shut by the force of the water at the upper part of thebucket; so that the bucket is drawn up full of the lowest sea-waterto which it has descended. When the bucket is drawn tip, themercurial thermometer lixed in it is examined; but great care mustbetaken to observe the degree at which the mercury stands, beforethe lower part of the thermometer is taken out of the water in thebucket, lest it be affected by the different temperature of the air.

To keep the bucket in a right position, there are four cords fixedto it, reaching about three feet below it; to which the sinkingweight is fixed. The result of several trials with this gage was,that when it was letdown to different depths, from 360 feet to5,346 feet, in lat. 25. 13. N. and Ion. 25. 12. W. it was discoveredby the thermometer, that the cold increased gradually in pro-portion to the depths, till it descended to 3,900 teet, viz.near three-fourths of a mile, whence the mercury in tlte thermometer canieup at 53°; and though it afterwards sunk to 5,346 feet, e. a mileand 66 feet, it came tip no lower: the warmth of the water uponthe surface, and that of the air, was all that time 84° When thewater in tin* bucket was become of the same temperature with thaton the surface of the sea, equal quantities of both were weighedand tried by the hydrometer; that front below was found to bethe heaviest, and consequently the saltest. Dr. Hales was proba-bly led to the construction ot this sea-gage from an instrument in-vented by Dr. Hpok, and designed for the same purpose. SeePlate LXXVIII, fig. 2. This consists ofa square wooden bucketC, whose bottoms are so contrived, that as the weight A sinks the'iron B, to which the bucket C is fastened by two handles D, D, onthe end of which are the moveable bottoms or valves E E, andthereby draws down the bucket, the resistance of the water keep 9up the bucket in the posture C, whereby the water, whilst thebucket is descending, hath a free passage through it; whereas, assoon as the bucket is pulled upwards by the line F, the resistanceof the water to that motion beats the bucket downwards, andkeeps it in the posture G, wberehy the included water is keptfrom getting out, and the ambient water kept from getting in-Phil, Trans. N° 9, p. 149, and N° 24, p. 447, or Abr. vol. ii. P-260.

Gage, Sea , an instrument invented by Dr. Hales and D 1 "-Desaguliers for finding the depth of the sea; the description where-of is this: AB, Plate LXXVIII. fig. 3, is the gage-bottle,' 1 *which is cemented the gage-tube, Yf, in the brass cap at G. r I l’ eupper end of the tube F is hermetically sealed, and the open lowererni/is immersed in mercury, marked C, on which swims a snw'Jthickness or surface of treacle. On the top of the bottle is screw** 1a tube of brass 1IG, pierced with several boles to admit the waterinto the bottle AB. The body K is a weight hanging by its shan>

L, in a socket N, with a notch oil oue side at m, in which is fixe' 1the catch l of the spring S, and, passing through tlte hole L, in d 1 ®shank of the weight K, prevents its falling out when once h" n "

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