ALT 



wltli the fame velocity, it would reach to tlie tleplli of a 

 mile in fcvcntecn minutes, and rc:\fccnd in tlic like time. 

 Tins, liowivtr, might be a vague clUmate, until experience 

 has furnilhcd a rule. 



Tliis macliiue was tried in various depths in the Tiiamcs, 

 and anfwered very well, always retuining, and leaving the 

 ballall behind. It was afterwards tried near the Bernuid.is, 

 when feveral fhips,wcre in company ; but though a good 

 look-out was kept for three or four hours, it was not leen 

 to return. Hales's Statics, vol. ii. p. 328. 



Altitude of the fia's furfiice is not every wlicrc the 

 fame, as appears from tiie drift of currents letting llrong 

 out of one sea into another. 



Altitude of ihc mercury, in the barometer, is marked 

 by degrees placed on the face of that inllrumcnt, the varia- 

 tions of which are the chief objeft of barometrical obferva- 

 tions. 



The mean altitude of the mercury at London for every 

 day in feveral years is about 29.87 inches, and its varia- 

 tions are computed between 31 and 28 inches. Some fucr. 

 gettions have been made, as if the altitude of the mercury 

 were regularly greater in the morning than in the even- 

 ing ; at lead fomething of this kind was obferved to hold 

 for a confiderable time at Berlin. Hill. Crit. Rep. Lett, 

 torn. xiv. p. 239. 



Altitude of the pyramids in Egypt, was meafured fu long 

 ago as the time of Thalcs, by means of their fliadow, which 

 makes one of the firll geometrical obfervations we have an 

 exact account of. Phitarcli has given an account of the 

 manner of this operation, which, according to this author, 

 was done by erefting a ftaff perpendicular upon the end of 

 the (hadow of thj pyramid; and by two triangles made by 

 the beams of the fun, he demonllrated that there was the 

 iame proportion between the Ihadows as between the pyra- 

 mid and the ilaff. Stanl. Hill. Phil. p. i. p. 9. See Py- 

 ramid. 



Altitude, circles, paralkh, and quadrant of. See the 

 refpeclive articles. 



Altitude inflrumeni, equal, is that ufed to obferve a ce- 

 lellial objeft, when it has the fame altitude on the call and 

 weft fides of the meridian, or in the morning and afternoon. 

 This inllrument coiifills of a telefcopc about 30 inclies long 

 (with two vertical, and three or five horizontal wires in its 

 focus), lupported on the end of an iron bar or axis, 30 inches 

 long, and about an inch in diameter ; the axis being fjif- 

 tained in a vertical pofition by paffing through a hole in one 

 end of a brafs box, whofe other or lower end fuftains the 

 \ lower joint of the axis. The box, whicii is about 21 inches 

 long, with ends about four inches fquare, has only two 

 fides, which are fixed at right angles. Prom one of thefe 

 fides projeA four flat arms, with a hole in each, whereby the 

 box is, by fcrews, fixed in a vertical pofition to an upright 

 "" poft. On the lower end of the box hes a brafs plate, which 

 Aides in grooves, and can, by means of a fcrew, be gently 

 moved forwards or backwards ; in this plate is a fine punched 

 hole, to receive the fmooth conical point, into which the 

 lower end of the axis is formed. On the upper end of the 

 box are two plates, which Aide alfo in grooves ; and, by the 

 means of fcrews, can be gently moved fideways, till their an- 

 gular notches embrace the axis, which, in this part, is made 

 perfeftly cylindrical and very fmooth. To the upper part 

 of the axis is fixed, by its radius, a brafs fextant (or arch of 

 63°, to a radius of feven or eight inches) with the arch down- 

 wards, fo that the centre is juil above the top of the axis : 

 alfo a fpirit-levcl is fixed at right angles acrofs the axis, juil 

 under the arch, fo as to be clear of the upper end of the 

 box. To the under part of the telefcopc is fixed a brafs fe- 



A L T 



micircle, of the fame radius with the fcxt.Ant, bolli arche* 

 having a common ccntrc-pin. In the fcmicircic is a gix>ove 

 cut through the plate, parallel to its limb, to receive two 

 fcrew-pins, which go into the fextantal arch, near its ciidj ; 

 by tliele fcrew-pins the two ai-chci may he prclTid clofc, and 

 the telefcope (i^ed in any dcfired elcv.'nion, which miglit be 

 nearly afeertaiiied by gra'duatuig the fcmicircic, and pulling 

 a Vernier's fcale on tlie fextant. 



When this inllrument is ufed, the box is fixed to the poft, 

 and tlie axis put into the box, letting the conical point drop 

 into the punched hole ; the level is fcrcwed on, and the te- 

 lefcopc is annexed, obferviiig to infcrt the centre and arch- 

 pins ; then, by the help of the fcrew-platcs at the bottom 

 and top ends of the box, the vertical pofition of the axis it 

 correfted.fo that the fame end of the air-bubble in the level 

 rtiay ftand at the fame point through the >vliole revolution of 

 the axis, which will thereby be known to be then truly verti- 

 cal, fo that the telefcope will deferibc a parallel of altitude. 

 The tube, thus adjiiiled, is to be direfted to the fun or liar, 

 and fixed at the defired elevation, by preirnig the two archc* 

 together with the two fcrew-pins. This indrument i^ very 

 ulcful in adjulliiig clocks, &c. and compaiing rq„al 3\A ap- 

 parent time. 



ALTM.\NSTF,rN, in Geography, a market town of 

 Upper Bavaria, belonging to the family of Abenfpeig, 1 2 

 miles iiortli-cail of Ingollladt. 



ALTMORE, a town of Ireland, in the county of Ty- 

 rone and province of Ulller. N. lat. 54^ 34'. \V. long. 



ALTMUHL, a river of Upper Bavaria, which joins the 

 Danube near Kelheim. 



ALTMUHLMUNSTER, a commandcrv of the order 

 of St. John, in Upper Bavaria, in the dillrid of Rilden- 

 bnrg. 



ALTOBASCO, in Geography, the name given to the an- 

 cient city of Colopiion, in Ionia. 



ALTOMUNSTER, a market town of Upper Bavaria, 

 which has an abbey of nuns of the order of St. Bridget. 



ALTO Isf Basso, or in Alto ISj in Basso, in Law, 

 fignifies the abfolute reference of all differences, fmall and 

 great, high and low, to fome arbitrator, or indifferent perfon, 

 Paleat univeijis per ptjfentes, quod IViHiehiiui Tylar de Tritoii, 

 Iff Thomas Cower de yllmi/ire, pofiieruni fe in Alto fi" in 

 BalTo, in arbilrio quatucr hominum ; viz. de quadam querela 

 pendente inter eos in curia — Kos Isf lerram nojlram altc & bafsc 

 ipfius domini Regis fiippifuimus volunlati. 



Alto, high. As alto viola, the tenor violin, in oppufi. 

 tion to the bafs viol, to which inllrument or violoncello, the 

 tenor ftrings are tuned oClaves : as C. G=. D'. A'. The 

 following is the complete fcale on the tenor : 



G 



+ _-l-_.e-D-®-I-i:.-- 



D-9- 



::e:o: 





4tli btring, 



3d String. 2d String, id St 



nng. 



This indrument has been rendered much more important 

 of late years by quartets, and pieces made exprefsly for it than 

 it ufed to be in the old overtures and concertos, in which it 

 feldom had any melody alligned it. To fill up the harmony, 

 by the refufc of other parts, was its only employment. But in 

 the quartets of Stamitz, Boccherini, Giardini.'and, above all, 

 thofe of Haydn, it has been brought fully into aflion, and 

 enjoyed equality. 



Alto Relievo, in Sculpture, a rcprcfentation of figures and 



Other objedls againll a flat furfaee or back-ground ; diffetB 



5 H 2 from 



\ 



