# Circular

## equal, called and centesimal

CIRCULAR The supposed number of days in the year early led to the division of the circle into 300 equal parts, for use in astronomi cal instruments. A knowledge of the regular hexagon probably led to the further division of 300 degrees into six parts of 00 degrees each. The Babylonians divided each degree 00 equal parts, and each subdivision into 00 equal parts. thus producing the sexagesimal scale. (See NoTATIoN.) Thu, the circumference of a circle is divided into 300 equal parts, called degrees; each degree into 60 equal parts, called minutes; and each minute into 60 equal parts, called seconds. Further divisions are better represented by decimal fractions. The circle is also commonly divided into four equal parts of 90 seconds each, called quadrants. By con necting the centre of a circle with the points of equal division on the eirolonfc.rence, equal unit angles are formed, whose magnitude is in dependent of the length of the radius: pro during an angle measure. the basis of the pro

tractor (q.v.). For scientific purposes, however, it would he more convenient to divide a quadrant into 10) equal parts, called grades. and each of these into 100 equal parts, called centesimal minutes. and each of these into 100 equal parts. called centesimal seconds. This plan, attempted in France as part of the metric system, is known as the centesimal division of the circle. For ex ample, 3s 45' 17" (read 3 grades, 45 centesimal minutes, and 17 seconds) may be written 3.4517. To translate this into sexa gesitnal notation, 3r equals 3 = 2.7°, 45 centesimal minutes 45 X = 0.405' or 0.00075'; and so on. The sexagestual system is, however, so well established that the centesimal has only very recently, in France, come to take important rank.