C A L 



ftuJying and copying tlie works of eminent mafteVs. His 

 rliolen fubjefti were fea-porcs and lantlfcppes, cfpccinlly 

 vievvs about Rome and Vciiice, which he dcliajrcd and exe- 

 cuted with truth, nature, and cl.gance. His volume of 

 perfpeftive views of Venice, etehed with aqna-fortis, evince 

 his tnlle and abihties. He died in I/15. I'ilkington. 



CALIBER, or Calliper, in a general fenfe, denotes the 

 extent ot any round thing in thltkiitfs, or diameter. 



In whieh fenfe we fay, a cclnmn is of the fame caliber as 

 another, when they are both ofiiie fame diameter. 



Caliber more pavticulaily denotes the bore, or width of 

 a piece of ordnance, or other fire-anns ; or the diameter of 

 the mouth thereof; or tlie ball it carries. 



The caliber is the rule by which all the parts of a cannon, 

 or mortar, as well as of if? carriage, are proportioned. 



Calibi;r-/-o/,',;/i.j^j-, a fort of compares made vvith arched 

 legs, to take the diameter of convex or concave bodies. 



Caliber-compafles are ch\efly ufed by gunners, for taking 

 the diameters of the feveral parts of a piece of ordnance, or 

 of bombs, bullets, S:c. Their legs are therefore circular, 

 and move on an arch of brafs, whereon are marked the in- 

 ches and half-inches ; to fhew how far the points of the com- 

 pares are opened afnnder. 



Some are alfo made for taking the diameter of the bore of 

 a gun or mortar. 



The gaugers alfo fometimes ufe calibers to embrace the 

 two heads of any calk, in order to find its length. 



The caliber, ufed by carpenters and joiners, is a piece of 

 board notched tria:igular-wife in the middle, for the taking 

 of raeafure. 



Caliber, CALinER-n/Zi?, or Guntier^s Callipers, is an 

 inftrument, wherein a right line is fo divided, as that the 

 firll part being equal to the diameter of an iron or leaden 

 ball of one pound weight, the other parts are to the firll as 

 the diameters of balls of two, three, four, &c. pounds, are 

 to the diameter of a ball of one pound. The caliber is ufed 

 by engineers, from the weight of the ball given to deter- 

 mine its diameter, or calihei- ; or vice verfa. 



The gunner's callipers confift of two thin plates of brafs 

 joined by a rivet, fo as to move quite round each other: its 

 length from the centre of the joint is between fix inches and 

 a foot, and its breadth from one to two inches : that of the 

 nod convenient fize is about nine inches long. Many 

 fcales, tables, and proportions, Sec. may be introduced on 

 this inftrument ; but none are efll-ntial to it, except thofc 

 for taking the caliher of (hot and cannon, and for mea-' 

 furing the magnitude of faliant and entering angles. The 

 n-.oit complete callipers is exhibited Tab. Giiiirifry, Jit;. 2. 

 the furnittire and ufe of which we fliall now briefly defcribe. 

 Let the four faces of tliis inftrument be dillingnifhed by the 

 letters A, B, C, D ; A and D cnnfid of a circular head and 

 kg ; B and C confift only of a leg. 



On the circular liiad adjoining to the leg of the face A 

 are divifions denominated /Lot didmeters, which (hew the 

 diftance in inches and tcntlis of an inch of the points of 

 tlie callipers when they are opened ; fo that if a ball not 

 exceeding ten inches be introduced between them, tlie bcvil 

 edge E marks its diameter among th< fe divifions. 



On the circular bcvil part E of tlie face B is a feale of 

 divifions diftinguiflied by lb. w.i^ht r,f iron fiof. When the 

 d'ameter of any ftiot is taken between the points of the cal- 

 lipers, the inner edge of the leg A (liews its weight in 

 avoirdupoife pounds, provided it be lb. h, I, l|. 2. 3i «l> 

 ^\, 6, 8, 9, 12, 16, iS, 24, 2^, ,52, 36, or 42 ; the figures 

 nearell the bevil edge anfwcring to the lliort lines in the 

 fcale, and tliofe behind them to the longer ftrokes. This 

 fcale is conftructcd on the folh:iwing geometrical theorem, 



Vol. V. 4 



C A L 



\iz. that the weights of fjiiiercs are as the ciibei of th.ii 

 diameters. 



On the lower part of the circular iicad of the f,\ce A is a 

 feale of divifions marked bores nf \;m:s ; for the life of which, 

 the legs of the calhners are Hipped acrofs each other, till 

 the Heel points touch the concave furfiTe of the gun in its 

 grenteft breadih ; then the bevil edge F of the face \\ will 

 cut a divifion in the fcale ihewing tlic diameter of the boie 

 in inches and tenths. 



Within t!ic feales of Jliol and bore diameters on the circu- 

 lar part of A, are divifions marked /i^um.'r/v ; the inner 

 figures i, |i, ,^, 54., 8, J2, iS, 26, .56, conefpond to 

 the lorgeft lines ; and the figures i, 2, 4, 6, 9, 16, 24, 3:, 

 42, to tlie (liort ftrokes. When the bore of a gun is taken 

 between the points of the callipers, the bevil edge F will 

 either cut or be near one of thefe divifions, and (hew tht 

 weight of iron (hot proper for that gun. 



On the upper half of the circular head of the face A arc 

 three concentric fcales of degrees ; the outer feale confiftiiig 

 ot iSo degrees numbered from right to hft, 10, 20, &c. 

 the middle numbered the contrary way, and the outer feale 

 beginninfi; at the middle with o, and numbered on each 

 fide to (,o degrees. Thefe fcales ferve to take the quantity 

 of an angle, either entering or faliant. For an entering, oi- 

 internal angle, apply the legs of the callipers fo that its out- 

 ward edges coincide with the legs of the given angle, the 

 degree cut by the bevil edge F in the outer fcale fliews the 

 mcafure of the angle fought: for a faliant, or external 

 angle, (lip the legs of the callipers acrofs each other, fo that 

 their outward edges may coincide with the legs forn.ing the 

 angle, and tlie degree marked on tlie middle Rvle by the 

 bcvil edge E will fliew the meafnre of the angle required. 

 The inner fcale will ferve to determine the elevation of can- 

 non and mortars, or of any oblique plane. Let one end 

 of a thread be fixed into the notch on the plate B, and 

 any weight tied to the other end : apply the ftraight fide of 

 the plate A to the fide of the body wliofe inclination is 

 fought, hold it in this pofition, and move the plate B, till the 

 thread falls upon the line near the centre maiked Per[>. Then 

 will the bevil edge F cut the degrees on the inner fcale, 

 fliewing the inclination of that body to the hori2oii. 



On the face C near the point of the callipers is a little 

 table fliewing the proportion of troy ami avoirdupoife 

 weights, by which one kind of weight may be caiily reduc- 

 ed into another. 



Near the extreme of the face D of the callipers, are two 

 tables fliewing the proportion between the pounds weight 

 ot Eondon and Paris, and alfo between the lengths of the 

 loot meafure of England and France. 



Near the extreme on the face A is a table containing four 

 rules of the circle and fphere ; and geometrical figures 

 with numbers annexed to them : the firlt is a circle includ- 

 ing the proportion in round numbers of the diameter to its 

 circumferenec ; the fecond is a circle infcribed in a fquare, 

 and a fquare within that circle, and another circle in the 

 inner fqnarc : the numbers, 28, :2, above this figU'e, exhibit 

 the piopoition of the outward fquare to the area of the 

 inleribed ciicle ; and the numbers 14, 1 i, below it, fliew the 

 proportion between the area of the infcribed fqnarc 'and the 

 area of its infcribed circle. The third is a cube infciib-.d 

 in a fphete ; and the number S9J flicws that a cube of iron, 

 infcribed in a fphere of J 2 inches in diameter, weighs 8yV. 

 The fourth is a fphere in a cube, and the number 24;, 

 expren"es the weight in pounds of a fphere inrcribed in a 

 cube whofe fize is 12 inches : the fifth reprefciUs a cylinder 

 and cone of one foot diameter and height : the luimlx r in 

 the cylinder (hews, that an iron cylinder of that dianietf r 

 5 F a::d 



