EXPLOSION, in physics, is properly applied to the going off of gun-powder and the report made thereby. Hence it is used to express such sudden actions of bodies as generate air instantaneously. EXPONENT, in algebra, the same with index. and by which we are enabled to distinguish them. It is unnecessary in this place to say more either on colour in particular, or experimental philosophy in general. The different subjects of this collective article are particularly treated under their proper names, in the order of the alphabet: the reader will therefore turn, as he has occasion, to ACOUSTICS, CATOPTRICS, CHROMATICS, DIOPTRICS, HYDROSTATICS, MECHANICS, OPTICS, PNEUMATICS, ELECTRICITY, MAGNETISM, &c. &c. &c. — Also AIR, ATMOSPHERE, BURNING-GLASS, COLD, COLOUR, CONGELATION, EVAPORATION, FIRE, FLAME, FLUIDITY, HEAT, IGNITION, LIGHT, SOUND, STEAM, WATER, WIND, &c. E X P See ALGEBRA, n° 9. EXPONENT is also used in arithmetic, in the same sense as index or logarithm. EXPORTATION, the shipping and carrying out of the kingdom wares and commodities for other countries. See the articles COMMERCE, TRADE, and SHIPPING. EXPOSING of CHILDREN, among the ancients, a barbarous custom of laying down children by the sides of the highways, and other places most frequented, where they were left at the mercy of the public, and where it behoved them to perish unless taken up and educated by charitable and compassionate persons. Many exposed their children, merely because they were not in a condition to educate them; and as for those who exposed them for other reasons, they commonly did it with jewels, with a view no doubt to encourage those who found them to take care of their education if alive, or give them human burial if dead. EXPOSITION, in general, denotes the setting a thing open to public view: thus it is the Romanists say, the host is exposed, when shewn to the people. EXPOSITION, in a literary sense, the explaining an author, passage, writing, or the like, and setting their meaning in an obvious and clear light. EXPOSITOR, or EXPOSITORY, a title given to small dictionaries, serving to explain the hard words of a language. EXPOSTULATION, in rhetoric, a warm address to a person, who has done another some injury, representing the wrong in the strongest terms, and demanding redress. EXPOSURE, in gardening, the situation of a garden-wall, or the like, with respect to the points of the compass, as south or east. See GARDENING. EXPRESSED OILS, in chemistry, such oils as are obtained from bodies only by pressing. See OIL. EXPRESSION, in rhetoric, the elocution, diction, or choice of words in a discourse. See LANGUAGE, ORATORY, and POETRY. EXPRESSION, in music. See COMPOSITION. EXPRESSION, in painting, a natural and lively representation of the subject, or of the several objects intended to be shewn. The expression consists chiefly in representing the human body and all its parts, in the action suitable to it: in exhibiting in the face the several passions proper to the figures, and observing the motions they impress on the external parts. See PAINTING, n° 15.