Other varieties of sealing-wax are made thus :—To make red, take of camphor, 4 oz.; Venice turpentine, 2 lbs.; vermilion, 11 lb. , rectified spirit of wine, 16 oz. Dissolve the camphor, first, in the recti fied spirit of wine in a suitable vessel, over a slow fire, taking care that no flame touches the evaporating spirit : then add the shell-lae ; and when that has become of an unirc' inn smoothness by a moderate application of heat, add the Venice tur pentine, and lastly, the vermilion, which should be passed. through a hair-sieve held over the melted mass, in order that it may not get into clots. When the whole is well incorporated it may be formed into sticks.
It is usual to weigh out the soft wax into balls, and roll them on a table into the lengths desired, and then flatten them by pressure. They are polished by being held over a charcoal fire in a chafing-dish, then drawn over a tallow candle and rubbed with soft leather. Black mar. Instead of vermilion, em ploy lampblack. Black resin is also often used in about one-third the quantity of the shell-lac, thus : Take of camphor, 1 oz.; 21 lbs. ; black resin, 11 lbs.; oil of turpentine 8 Oz. ; rectified spirit of wine, 8 oz. ; lampblack, 4 oz. Dissolve the camphor in the rectified spirit of wine, then add the shell-lac, to which pour the resin previously incited and mixed with the oil of turpentine • using, of course, a moderate heat, anetaking care that no flame touches the melting matters. SECTOR. A mathematical instrument, of considerable use in making diagrams, laying clown plans, &c. Its principal ad vantage consists in the facility with which it gives a graphical determination of proportional quantities ; and hence it is called by the French the compass of pro portion.
The instrument consists of two rulers (generally of brass or ivory), represent ing the radii of a circular are, and mov able round a joint, the middle of which forms the centre of the circle. From this
centre there are drawn on the faces of the rulers various scales ; the choice of which, and the order of their arrangement, May be determined by a consideration of the uses for which the instrument is chiefly intended. The scales usually put on sec tors are of two kinds—single and double ; that is to say, such as are drawn only on one of the limbs, and such as are drawn on both limbs. The first kind, however, (comprising, for example, a line of inches, of chords, sines, logarithms, &e.) are not peculiar to the sector, but are merely placed there for convenience, and may be used whether the instrument is shut or open. Of the lines repeated on both limbs, the principal are the following :— 1. A line of equal parts, by which, with a pair of compasses, we aro enabled, on the principle that similar triangles have their homologous sidesproportional, to find a third proportional two given lines, a fourth proportional to three given lines, to diminish a line in any given pro portion, &c. 2. A scale of chords, which enables us to protract an angle of any giv en number of degrees, to find the degrees which any given angle contains, to cut off an are of any given magnitude from the circumfezence of a given circle, &o. 8. Scales of sines, tangents, and secants, whereby the length of the trigonometrical lines corresponding to a given arc of a circle of any radius are determined. 4. A line of polygons, whereby the propor tional length of the side of any regular polygon (of not more than 12 sides) to the radius of the circumscribing circle is found.
The sector may be used in trigonometry for obtaining a rough solution of all the cases of right-angled plane triangles ; and it is also conveniently applied to the construction of various geometrical pro blems.