14 



EXPLANATION OF SCIENTIFIC TERMS. 



f angled sector. When the angle contained 

 between the radii is a right angle, the 

 sector is a quadrant, and is so called. A 

 sector is also the name given to a mathe- 

 matical instrument, composed of two flat 

 rulers connected with a joint, which allows 

 them to open in the form of radial lines, 

 so as to include a sector. 



SEGMENT OF A CIRCLE is any por- 

 tion cut off by a straight line. Thus, in 

 the preceding figure, E F G is a segment 

 cut off by the line E F. When this line 

 passes through the centre it divides the 

 circle into two equal segments, or semicir- 

 cles. 



SEMI-TRANSLUCENT. See Diapha- 

 nous. 



SEMI-TRANSPARENT. See Diapha- 

 nous. 



SHEAR-STEEL (so called because fitted 

 for making clothiers' shears, scythes, &c.) 

 is prepared by laying several bars of com- 

 mon steel together, and heating them in a 

 furnace until they acquire the welding 

 temperature. The bars are then beaten 

 together with forge hammers, after which 

 they are drawn anew into bars for sale. 



SILEX. See Gloss. I. 



SINE. See Angle. 



SINES, LAW OF THE. See Reflective 

 Power. 



SODA. See Alkali. 



SOLIDS. See Gloss. I. 



SOLID OF LEAST RESISTANCE. See 

 Conoid. 



SOLUTIONSee Gloss. I. 



SOUND. See Gloss. I. 



RAYS OF. See Reflexion. 



SPAR. See Gloss I. 



SPAR, ADAMANTINE. See Corundum. 



ICELAND. See Calcareous Spar. 



SPECIFIC denominates any property that 

 is not general, but is confined to an indivi- 

 dual or species. 



GRAVITY. See Gravity, Spe- 

 cific. 



, HEAT. See Caloric, Specific. 



SPECTRA, OCULAR._See Ocular Spec- 

 tra. 



SPECTRUM, PRISMATIC. See Pri*- 

 mafic Spectrum. 



SPECULUM. See Mirror. 



SPHERE. See Gloss. I. 



SPHERICAL ABERRATION. See 

 Gloss. I, 



SPHEROID. See Gloss. I. 



SPIRAL. See Gloss. I. 



SPIRIT OF WINE. See Alcohol. 



STATICS is that division of the science of 

 mechanics which considers bodies as in- 

 fluenced by forces that are in equilibrium. 

 It therefore treats of bodies at rest. The 

 word is formed from the Greek statos, 

 standing still. What belongs to statics is 

 statical. 



STEAM is generally used to signify the 

 visible cloudy vapour arising from water, 

 and which at low temperatures is sup- 

 posed to be the consequence of a chemical 

 solution of water in air; but steam, as it 

 is used in the arts, denotes water, in an 

 elastic form, at or above the temperature 

 of the boiling point, when it is invisible. 



STEAM-TIGHT is that degree of closeness 

 which, in any particular case, prevents 

 the escape of steam. 



STEEL. See Carbon. 



TEMPER OF. The different tem- 

 pers, or degrees of hardness, of rigidity, 

 or of elasticity, are given by means of the 

 different degrees of heat to which the 

 metal is exposed in the operation. 



STEELYARD. See Balance. 



STRAIGHT LINE, the same as a right 

 line. See Curve. 



SUCTION. The action of sucking is per- 

 formed by the child's making a vacuum 

 in its mouth, which exhausts the air from 

 the pores of the nipple ; and the milk is 

 consequently ejected from the breast by 

 the unresisting elasticity of the air within. 

 The raising of liquids through a tube, by 

 means of a piston which lifts and sustains 

 the weight of the atmosphere from that 

 part of the well which is covered with the 

 tube, leaving it to press on the other parts 

 of the surface, is also, metaphorically, 

 termed suction. 



SYNTHESIS. See Analysis. 



TABASHEER. See Gloss. I. 



TANGENT. See Gloss. I. 



TELESCOPE, ACHROMATIC. See 

 Gloss. I. 



TEMPERATURE. See Gloss. I. 



THERMOMETER. See Gloss. I. 



THERMOSCOPE, a name given by 

 some inventors to their particular kinds 

 of thermometers ; as pyroscopes are names 

 of some sorts of pyrometers. 



TOPAZ. See Corundum. 



TORSION-BALANCE, a delicate elec- 

 trometer, so called because its principle 

 consists in the torsion or twisting of a silk 

 fibre. 



TORRICELLIAN VACUUM. See 

 Gloss. I. 



TOURMALINE. See Gloss. I. 



TRANSLUCENT. See Diaphanous. 



TRANSPARENT. See Diaphanous. 



TRANSVERSE DIAMETER. See 

 Gloss. I. 



VALVE. See Gloss. I. 



VAPOUR. See Gloss I. 



