COM 



COM 



Feed on her damask cheek: she pined 

 in thought, 



And sat like Patience on a monu- 

 ment, 



Smiling at Grief." 



COMPARTMENT, or COMPART- 

 MENT, in general, is a design composed of 

 several different figures, disposed with 

 symmetry, to adorn a parterre, a ceiling, 

 &c. A compartment of tiles, or bricks, 

 is an arrangement of them, of different 

 colours, and varnished, for the decoration 

 of a building. Compartments, in gai'den- 

 ing-, are an assemblage of beds, plats, 

 borders, walks, &c. disposed in the most 

 advantageous manner that the ground 

 will admk of. Compartments in heraldry 

 are otherwise called partitions. 



COMPASS, or mariner's compass, an in- 

 strument whereby the ship's course is de- 

 termined. See MAGNETISM. 



COMPASS is also an instrument in sur- 

 veying of land, dialling, &c. whose struc- 

 ture is chiefly the same with that of the 

 mariner's compass; and,like that, consists 

 of a box and needle ; the principal differ- 

 ence being this, that instead of the nee- 

 dle's being fitted into the card, and play- 

 ing with it on a pivot, it here plays alone. 

 See SURVEYING. 



COMPASS dials are small horizontal di- 

 als fitted in brass or silver boxes for the 

 pocket, to show the hour of the day, by 

 the direction of a needle, that indicates 

 how to place them right, by turning the 

 dial about till the cock or style stand di- 

 rectly over the needle, and point to the 

 northward ; but these can never be very 

 exact, because of the variations of the 

 needle itself. 



COMPASSES, or pair of compasses, a ma- 

 thematical instrument for describing cir- 

 cles, measuring figures, &c. They consist 

 of two sharp pointed branches or legs of 

 iron, steel, brass, or other metal, joined 

 at top by a rivet, whereon they move as 

 on a centre. 



COMPASSES of three legs are, setting 

 aside the excess of a leg, of the same 

 structure with the common ones : their 

 use being to take three points at once, 

 and so to form triangles ; to lay down 

 three positions of a map to be copied at 

 once, &c. 



COMPASSES, beam, consist of a long 

 branch or beam, carrying two brass cur- 

 sors, the one fixed at one end, the other 

 sliding along the beam, with a screw to 

 fasten it on occasion. To the cursors 

 may be screwed points of any kind, 

 whether steel for pencils, or the like. It 



is used to draw large circles, to take great 

 extents, &c. See INSTRUMENTS, mathema- 

 tical. 



COMPASSES, caliber. See the article CA- 

 LIBER. 



CoMPASSKs,cZocfc7wafcers',are joined, like 

 the common compasses, with a quadrant 

 or bow, like the spring compasses; only 

 of different use, serving here to keep the 

 instrument firm at any opening. They 

 are made very strong, with the points of 

 their legs of well-tempered steel, as be- 

 ing used to draw lines on pasteboard or 

 copper. 



COMPASSES, elliptic, consist of a cross 

 with grooves in it, and an index which is 

 fastened to the cross by means of dove- 

 tails that slide in the grooves ; so that 

 when the index is turned about, the end 

 will describe an ellipsis, which is the use 

 of these compasses. 



COMPENSATION, in horology, is a 

 contrivance in the pendulum of a clock, 

 by means of which, while the expansion 

 from increase of temperature depresses 

 the centre of gravity of some of the vi- 

 brating parts, other parts are made to 

 ascend nearer the centre of suspension, 

 or else to draw up the pendulum, so as 

 to preserve the centre of oscillation of 

 the compound pendulum at an invariable 

 distance; and in consequence to keep 

 all the vibrations to the same time. 



Compensation pendulums have the 

 part which expands upwards made either 

 of brass or zinc, or some very expansible 

 metal, while the descending parts are 

 usually iron or steel, and some of these 

 have leaves or machinery in their con- 

 struction : in others the compensation- 

 part does not vibrate, but serves to alter 

 the length of a simple pendulum; and 

 in others a fluid is used, most commonly 

 mercury. See HOROLOGY and PENDU- 

 LUM. 



COMPENSATION balance. See HO- 

 ROLOGY. 



COMPLEMENT, in astronomy, the 

 distance of a star from the zenith : or 

 the arch comprehended between the 

 place of the star above the horizon and 

 the zenith. 



COMPLEMENT, in geometry, is what re- 

 mains of a quadrant of a circle, or of 90 

 after any certain arch has been taken 

 away from it. Thus, if the arch taken 

 away be 40, its complement is 50 : be- 

 cause 50 -f 40 = 90. The sine of the 

 complement of an arch is called the co- 

 sine, and that of the tangent, the cotan- 

 gent, &c. 



