Ill 



COMPASS, NOTATION OF. 



OOMPoslTlnX. 



bearing* have been taken by the Lite secretary of the Compass 

 Committee at Liverpool, while a ship ha* been twinging with 

 the tide ereo in so quick and rtrong a river a* the Money. 



2. Either register the error *o found in one of the admiralty fonni 



of graphic delineation ,s : , A Smith'*), or adjust the nhifting 

 magneU and soft iron by the astronomer royal'* method, by 

 the asawUnue of Gray's or any other apparatus for eflecting 

 thu object. [COMPASS, TIIK MARINER'S.] 



3. Let the ahip occasionally yaw a few points from her course at 



least once a day, using the spherograph, and in caae of suspected 

 bad weather, up to the last moment at which a heavenly body 

 b visible. 



By following the above plan the compass need no longer be a source 

 of anxiety to an officer of a ship ; for instead of his having, as at 

 present, to depend on an erroneous system of adjustment made in port 

 perhaps many months before, or by the working of an azimuth, for 

 which be cannot always get an altitude, he can dispense with both 

 the** method*, and avoid all calculations or complexities whatsoever, 

 whenever any heavenly body is visible. If by night, be would use 

 the star's distance in time from the meridian of the place as if it were 

 in the spherograph apparent time. 



From the extreme simplicity, infallibility, and rapidity of the above 

 method, it may be suggested that, in passenger over sea steamers, 

 the compass ought to be checked met in every vatcli ; for this 

 purpose a common compass, fitted with Captain Robertson's patent 

 " deviation detector" [BEARING], would, with the spherograph, be all- 

 sufficient. 



COMPASS, NOTATION OF. The notation of the mariner's com- 

 pass is very simple. If we divide a circle into four equal parts, each 

 of the points which separate those parts may be called cardinal. Pliny 

 called one of. these the canio mvnili, or the pole of the world, meaning 

 the north pole. Another ancient author speaks of the eardo cceli, or 

 the pole of the heavens, meaning also the north pole ; while Quintilian 

 sposVn of the /our as the quatuor cardinet mundi. Hence, by common 

 consent, the north, east, south, and west are called " cardinal points." 



The formation of the compass card will be easily understood by the 

 following : 



Let N.E.S.W. represent the cardinal points. The point midway 

 between them is formed by combining the letters ; thus, taking the 

 quadrant or quarter of a circle which lies between N. and E., the 

 intermediate point will be called N.E. If we halve thin distance, 

 N. and N.E., we call the middle point N.N.E. If we halve now the 

 distance, N. and N.N E., we call it N. b. E. (or north by east, or north 

 tmcardt east, for any further combining of letters would be incon- 

 venient). In like manner we divide N.E. and E., and the intermediate 

 point will of course be E.N.E. (the nearest cardinal point always stands 

 first when we combine the letters) ; and again, halfway between E.N.E. 

 and E. would be E. b. N. (or east towards north). It need only to be 

 remembered that the cardinal points, and the midway points between 

 them, such as N.E., S.E., N.W., S.W., always have the word " by" or 

 " b." in the points next to them. The other three quadrants are 

 formed in precisely a similar manner. We tints find the circle divided 

 into 32 parts or points ; and as the whole circumference of a circle is 

 divided into 360 degrees, 360 divided by 32 will give 11" 15', or 11J 

 dryno, as the angle which each point makes at the centre of the 

 compass. 



. When using a compass card, the observer should always consider 

 himself as at the centre of it, and not outside the circle ; for the centre 

 of the compass card represents the point of the earth on which he is 

 standing, and the visible horizon may be considered to be represented 



by 'the outer rim of the card, on which the degree* are generally 



::. ,!'*..! 



The direction in which an object lie* 1* called iu bearing. [ BEA i 



OOKPA88B8 tl .. pp ; -.>. nyt tu iiii m- 

 patten, instrument* by which we compass or go round a space. We 

 shall here only (five such a general notion of different kinds of con- 

 struction* a* will perhaps suggest the most convenient for any par- 

 ticular purpose. 



1. Common Cntnftattei, or Divider*. These are simply two pointed 

 legion a common pivot, for transferring distances. Kor drawing a 

 circle the lower end of one of the legs is removed, and it* place 

 supplied by a holder for a pencil, or by a steel pen. 



_ I loir C'im/KUta. One of the legs ha* a part attached to the upper 

 part by a spring, so that by means of a screw a very small motion may 

 be given to the lower end. It is convenient for very accurate dividing, 

 but must be used with care. 



3. Triangular Compauei. These have three legs and two pivots, so 

 that the three points of a triangle can be at once transferred. Thin is 

 useful only in rough work, as the instrument is difficult to handle. 



4. Proportional Comjxiut*. These consist of two dividing compasses 

 with a common pivot, which, when open, present vertically opposite 

 angles ; consequently, the intervals between the point* of one and the 

 other are in the same proportion as the legs of one to the legs of the 

 other. The pivot is a clamping screw, which can be transferred along 

 the interval between the pairs of points, and a scale points out how to 

 adjust the instrument so as to alter any line, or surface, or solid, in a 

 given proportion. These compasses sometimes have an appanit 

 slight adjustment; but on the whole we consider it as an instrument 

 for rough work. 



5. Beam Compattes. This instrument is a cylindrical bar, perpendi- 

 cular to which, with clamping screws, slide a point and a pencil. The 

 use of it is to describe large circles, or to measure large distances, the 

 common compasses being very liable to slip when opened very wide. 

 It is a safe and sure construction. 



6. There is a method of describing a small arc of a very large circle, 

 as follows : An elastic rod of metal is furnished with a rigid 

 which it can be drawn up by screws, so that the rod shall form an arc, 

 the chord of which is a port of the bar. This may be adjusted so as to 

 pass through three given points nearly in the same straight line, and 

 though the curve then described by guiding the point of a pencil along 

 the rod be not exactly an arc of a circle, yet, for all small flexures, it 

 will come sufficiently near for practical purposes. 



7. Caliper Compassa, or callipers, ore compasses intended to measure 

 the calibre or diameter of round bodies, and are formed with curved 

 legs, knobbed instead of pointed. Being opened until the body to be 

 measured can only just pass through them, the distance between the 

 two internal extremities of the knobs is of course the diameter of 

 the body. 



Many other species of compasses have been constructed, but the 

 above are the principal ones in common use. [ELLIPTIC COMPARES.] 



COMPLEMENT, that magnitude which, with another, makes up a 

 given magnitude. This is the general meaning of the term ; but thn 

 most usual specific uses are as follows : Complements of the paralUlo 

 grams about the diagonal of a parallelogram : through a point in the 

 diagonal draw parallels to the sides ; the whole is then divided into 

 two parallelograms on the diagonal, and two which only touch the 

 diagonal at one angle. The latter pair are called by Euclid comple- 

 ments to the former. 



The complement of on arc or angle is the arc or angle by which it 

 falls short of a quadrant or a right angle. 



The complement of a logarithm is the number by which a logarithm 

 falls short of 10 : thus comp. log. 2 is 10 '30103 or 9'69897. 



The arithmetical complement of a number is the number by which 

 it falls short of the next higher decimal denomination. Thus, ar. co. 

 936 is 1000-936, or 64; arith. comp. of 83 is 100-83, or 17. 

 Beginning from the left, subtract every figure from 9, up to the last 

 significant figure, which subtract from 10. 



For the complement of life, see DK MOIVRE'S HYPOTHESIS. 



COMF1. KM KNTAKY COLOURS. [ LIGHT.] 



COMPLUTENSIAN POLYGLOTT. [Bim.K.] 



or NUN MiMl'dS, MKXTIS. [INSANITY.] 



COMPOSITE ORDER. [COMWN.] 



COMPOSITION. In the gradual progress of mathematical l.m- 

 guage, this word has acquired a general meaning, as follows : Any one 

 magnitude is said to be compounded of two others, when it produces 

 the same effect as the other two put together. For instance, if wo 

 increase a length in the proportion of 3 to 7, and then increase the 

 result in the proportion of 2 to 5, the original line U increased in the 

 proportion of 3 x 2 to 7 x 5, or of 6 to 35. Hence the proportion of 

 6 to 35 is said to be the proportion compounded of (out of ) the pro- 

 portions of 3 to 7 and 2 to 5. 



The effects of which it is in our power to form a distinct conception 

 are of two kinds : 1. Those in which there are only two kinds imagi- 

 nable, and those two diametrically opposite, with one neutral inter- 

 mediate state. 2. Those in which the diametrically opposites have an 

 infinite number of intermediate gradations. Loss or gain of money is 

 an instance of the first ; change of direction of the second. If, at the 

 rate of an inch to a shilling, gains were measured northward from a, 



