ARCHIL, or ORCHIL ([.a]r´kil, or´kil), a red, violet, or purple colouring matter obtained from various kinds of lichens, the most important of which are the _Roccella tinctoria_ and the _R. fuciformis_, natives of the rocks of the Canary and Cape Verde Islands, Mozambique and Zanzibar, South America, &c., and popularly called dyer's-moss. The dye is used for improving the tints of other dyes, as from its want of permanence it cannot be employed alone; but the aniline colours have largely superseded it. Cudbear and litmus are of similar origin.
ARCHILOCHUS ([.a]r-kil´o-kus) OF PAROS, one of the earliest Ionian lyric poets, the first Greek poet who composed iambic verses according to fixed rules. He flourished about 700 B.C. His iambic poems were renowned for force of style, liveliness of metaphor, and a powerful but bitter spirit of satire. In other lyric poems of a graver character he was also considered as a model. All his works are lost but a few fragments.
ARCHIMAN´DRITE, in the Greek Church, an abbot or abbot-general, who has the superintendence of many abbots and convents. The title dates from the fourth century.
ARCHIME´DEAN SCREW, a machine for raising water, said to have been invented by Archimedes. It is formed by winding a tube spirally round a cylinder so as to have the form of a screw, or by hollowing out the cylinder itself into a double or triple-threaded screw and enclosing it in a water-tight case. When the screw is placed in an inclined position and the lower end immersed in water, by causing the screw to revolve, the water may be raised to a limited extent.
ARCHIMEDES ([.a]r-ki-m[=e]´d[=e]z), a celebrated ancient Greek physicist and geometrician, born at Syracuse, in Sicily, about 287 B.C. He devoted himself entirely to science, and enriched mathematics with discoveries of the highest importance, upon which the moderns have founded their admeasurements of curvilinear surfaces and solids. Archimedes is the only one among the ancients who has left us anything satisfactory on the theory of mechanics and on hydrostatics. He first taught the hydrostatic principle to which his name is attached, "that a body immersed in a fluid loses as much in weight as the weight of an equal volume of the fluid", and determined by means of it that an artist had fraudulently added too much alloy to a crown which King Hiero had ordered to be made of pure gold. He discovered the solution of this problem while bathing; and it is said to have caused him so much joy that he hastened home from the bath undressed, and crying out, _Eur[=e]ka! Eur[=e]ka!_ 'I have found it, I have found it!' Practical mechanics also received a great deal of attention from Archimedes, who boasted that if he had a fulcrum or stand-point he could move the world. He is the inventor of the compound pulley, probably of the endless screw, the Archimedean screw, &c. During the siege of Syracuse by the Romans he is said to have constructed many wonderful machines with which he repelled their attacks, and he is stated to have set on fire their fleet by burning-glasses. At the moment when the Romans gained possession of the city by assault (212 B.C.), tradition relates that Archimedes was slain while sitting in the market-place contemplating some mathematical figures which he had drawn in the sand.