Page:Cyclopaedia, Chambers - Volume 1.djvu/440

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Brutes Teem not to have this Faculty in any great degree : They have, probably, feveral Ideas diftina enough ; but cannot compare them farther than as tofomefenfibleGrcum- ftances annexed to the Objeas themfelves : The Power of comparing general Ideas, which we obferve in Men, we may probably^conjcaure they have not at all. See Abstract, General Terms'^ &c. m „ _

COMPARTIMENT, or COMPARTMENT, a Defign compos'd of feveral different Figures, difpos'd with Symme- try ; to adorn a Parterre, Plafond, Panes of Glafs, or lannels of joinery, the Squares of a Cieling, &c.

A Compartment of Tiles, is an Arrangement of white and red Tiles varnifli'd, 'for the Decoration of the Covering of a Roof. .

The Term Compartment is alfo ufed in Painting : Thus, we fay, all the Turhfh and Moorijb Paintings are only Com- partments : The fine Bindings of Books are in Compart- ments, Sic.

Compartiment, in Heraldry. See Partition. COMPARTITION, in Architeaure, the ufeful and graceful T>i(lribution of the whole Ground-Plot of an Edi- fice, into Rooms of Office, of Reception, or Entertainment. See Distribution, House, ci?c.

Compartition makes one of the great Divifions of the Art of Building. See Building.

COMPASS. The Mariner's, or Nautical Compass, is an Inllrumcnt ufed by Pilots, to direa the Courfe of their Ships. See Course, Navigation, f$c.

It confifts of a Box, which includes a magnetical Needle, that always turns to the North ; excepting for a little De- clination, which is various in various Places, and even at various Times, in the fame Place. See Needle, and Va- riation.

In the middle of the Box is fix'd a perpendicular Pivot, which bears a Card, or Paftboard, on whole upper Surface are defcrib'd feveral concentric Circles ; the outmoft of which is divided into 3S0 Degrees; the other into 32 Points, anfwering to the 32 Winds. See Wind.

In the Centre of this Card is fitted a Brafs Cone, or Cap, a little concave, which plays at liberty on the Pivot ; and along, in the Thicknefs of the Card, is fitted the Needle, which is covcr'd over with a Glafs, that its Motions may be obferv'd : The whole is inclos'd in another Box ; where it is furcaih'd by brafs Hoops, to keep the Needle horizontal. See it reprefented, Tab. Navigation, Fig. I.

The Needle, which is, as it were, the Soul of the Com- pafs, is made of a thin Plate of Steel, in form of a Lo- zenge : the middle being cut out, fo as to leave nothing but the Extremities and an Axis in the middle, to which the Cap is fitted. To animate, or touch it, it muff be rubb'd on a "ood Loadftone : that End intended for the North Point on the North Pole of the Stone, and that for theSouth Point on the South Pole. In rubbing it, care muft. be taken to beoin firrt in the middle of the Lozenge, drawing it gent- ly to "the acute Angle of the Lozenge intended for the North • never fuffering it to ftay at the End when arrived there, nor drawing it back again from the End to the Mid- dle, but rubbing it a fecond, and even a third time, in the fame manner as the firft, only beginning a little further and further from the North Point : Some fay, the Stone and Needle mull be fo difpofed as that the Line of the Rub be in the Direaion of the Meridian. See Magnet.

The Invention of the Compass is ufually afcrib'd to Fla- vio de Melphe, or Ftitvio Gioia a Neapolitan, about the Tear 1302 : and hence it is, that the Territory of (Princi- pato, which makes a part of the Kingdom of Naples, where he was born, bears a Compafi for its Arms.

Others fay, that Marcus (Pantos a Venetian, making a Journey to China, brought back the Invention with him in 1260 t What confirms this Conjcaure, is, that at firft they ufed the Compafi in the fame manner as the Cbinefe ft ill do ; i.e. they let it float on a little piece of Cork, inftead of fufpending it on a Pivot. 'Tis added, that their Emperor Chimngus, a celebrated Aftrologer, had the Knowledge of it 1 1 20 Years before Chrift. The Cbinefe only divide their Compafi into 24 Points.

Fauchet relates Tome Verfes of Guyot de "Provence, who lived in Francs about the Year 12CO, which feem to make mention of the Compafi under the Name of Ma'rrinette, or Mariner's Stone ; which fhewsit to have been ufed in France near too Years before either the Melphite or Venetian. The French even lay claim to the Invention from the Flower de Lis wherewith all Nations ftill dirtinguifh. the North Point of the Card.

With as much Reafon Dt.WttUlS afcribes it to the Englifb, from its Name Compafi, whereby moft Nations call it ; and which he obferves, is ufed in many Parts of England to fig- nify a Circle. . . •

'The life of the &«-Compass is obvious. For, the Courfe a Ship is to fail in, being known by the Chart ; and the Compafi fo placed, as that the two parallel Sides of the fcjuare Box be difpos'd according to the length of the Ship,

i. e. parallel to a Line drawn from the Head to the Stcr the Rudder is to be dircaed accordingly ; v.g. IftheCouria be found on the Chart between the South- Weft and Soud South- Wert, i.e. South- Weft V to the South : turn the Step fo as that a Line from the South- Weft, I South exacl.lv an fwer the Mark on the middle of the fide of the Box. This 'is all that is requir'd. See Sailing, Chart, &c.

Compass is alfo an Inrtrument of confiderable ufi- i n furveying Land, Dialling, &c. See Surveying, Dial- ling, ££c.

Irs Struaure, in the main, is the fame with that of the Mariner's Compafi ; confiding, like that, of a Sox and Nee- dle : The principal difference confifts in this, that inllead of the Needle's being fitted into the Card, and playing with it on a Pivot, it here plays alone ; the Card being drawn on the bottom of the Box, and a Circle divided into 360 Be. grees on the Limb. See Tab. Surveying, Fig. 1 5.

This Inrtrument is of obvious ufe to Travellers, to di- rea 'em in their Road ; and to Miners, to fhew them what

"y> yet

way to dig, 03c. But it has other Ufes, tho lefs eaf more confiderable.

1. To take the Declination of a Wall iy the Compass. Apply that fide of the Compafi whereon the North ismark'd along the fide of the Wall ; the Number of Degrees o'er which the North End of the Needle fixes will be the De- clination of the Wall, and on that fide : v. g. if the North Point of the Needle tends towards the Wall ; that Wall may be fiione on by the Sun at Noon ; if it fix over 50 Degrees, counting from the North towards the Eaft, the Declination is fo many Degrees horn South towards Eaft.

But fince the Needle it felf declines from the North to- wards the Weft, with us, 13 ; it muft be noted, that to re- trieve the Irregularity, 13 be always added to the Degrees jhewn by the Needle, when the Declination of the Wall is towards the Eaft : on the contrary, when the Declination is towards the Weft, the Declination of the Needle to be fub- traaed. See Declination.

2. To take an Jingle with the Compass. Suppofe the An- gle requir'd be DAE, (Tab. Surveying, Fig. 11.) apply that fide of the Compafi whereon the North is mark'd to one of the Lines A D ; when the Needle refts, obferve the De- grees at which its North Point ftands, which fuppofe 80 : fo many Degrees does the Line decline from the Meridian.

In the fame manner take the Declination of the Line AE, which fuppofe 215 ; fubtraa 8o° from 215, the Remainder is 13; ; which fubtraaed from 180, there will remain 45 ; the quantity of the Angle requir'd.

But if the difference berween the Declination of the two Lines exceed 180 ; in that Cafe, 180 muft be fubtracted from that difference : the Remainder is the Angle requir'd.

For the Method of laying this down on Paper. See Plot- ting.

Note, In meafuring Angles by the Compafi, there needs not any regard be had to the Variation; that being fuppos'd the fame in all the Lines of the Angles.

3. To take the Vlot of a Field by the Compass. Sup- pofe the Field A, B, C, D, E, (Fig. 12.) for the greater accuracy let there be two Sights fitted to the Meridian Line of the Compafi, place it horizontal, and thro' the Sights look along the Side A B, or a Line parallel to it; ap- plying the Eye to the Sight at the South-Point of the Com- pafi. Draw a rough Sketch of the Field by the Eye, and on the correfponding Line enter down the Degree to which the Needle points, which fuppofe 90 ; meafure the length of the Side, and enter that too, which fuppole ro Chain.

In this manner proceed with all the reft of the Sides of the Field ; the Sides which fuppofe 70,45,70,50,94 Chains; and the Angles which fuppofe 30,100,1 30,240,300 Degrees.

To protraS the Field, fet down the feveral Angles ob- ferv'd, one after another, and fubtraa the lefler from the next greater : thus will you have the quantity of the ieveral Angles, and the length of the Lines that include them. For the reft fee Plotting, and Protracting.

Note, All the Angles of the Figure taken together, mutt make twice as many right Angles, abating two ; if no Mil- take have been committed.

Azimuth Compass, differs from the common Scu-Comffi in this ; that there is faften'd, on the round Box wherein the Card is, a broad Circle AB, (Tab. Navigation, Fig- "■) one half whereof is divided into 90 Degrees, and thofe hib- divided diagonally into Minutes : b c is an Index moveable on b, having a Sight, b a, ereBed thereon, and moving on a Hinge. From the upper part of the Sight, to the middle of the Index, is faften'd a fine hypothenufal Lute String a e, to give a Shadow on a Line in the middle of the Index. The Circle A B is crofs'd ar right Angles with two Threads, from the Extremities whereof are drawn four Lines on the infide of the round Box : there are alfo four Lines drawn at right Angles to each other on the Card. The round Box fitted with its Card, graduated Circle, and Index, is hungm the brafs Hoops B B, and thole Hoops faften'd to the iquare Box CC. ^l,