Arch i me des, Principle

OF. ( Hydraul.) A well known principle in hydrostatics, the discovery of which is attributed to the celebrated philosopher whose name it bears. This important theorem may be thus defined: When a solid is immersed in a fluid, it loses a portion of its weight, and this portion is equal to the weight of the fluid which it displaces, that is, to the weight of its own bulk of the fluid. An experimental proof of this principle is thus obtained: - From one of the arms of a balance is suspended a hollow cylinder, having a cylindrical ma of any substance capable of exactly fitting into it, hanging from it by means of a thread. From the other arm of the balance hangs a scale-pan, into which weights are placed until the solid cylinder and the hollow one are exactly counterbalanced. Water is then poured into a ve el around the solid cylinder. until it is completely immersed; upon which the weights in the scale-pan will preponderate, the solid cylinder seeming to have lost a considerable portion of its weight. The balance will, however, be brought into equilibrio, if water be poured into the upper hollow cylinder until it is quite full. Now, as this hollow cylinder is of such a size that the solid ma exactly fits its interior, it follows that the water with which the hollow cylinder is filled is precisely equal in bulk to the solid cylinder; which proves that the apparent lo of weight suffered by the latter is precisely equal in weight to a ma of water equal in bulk to itself. This very ingenious method forms one mode-but not the most exact-by which the specific gravity of solids is ascertained. A wonderful story is told in connection with the discovery of this important principle. Hiero, king of Syracuse, intending to offer to the gods a crown, caused one to be manufactured of pure gold. When brought home. the crown appeared to be of full weight, but it was suspected that a part of the gold had been stolen, and a like weight of silver substituted.. Arch i me des was desired to investigate the supposed. fraud, and while engaged in solving the difficulty, he happened to enter the bath, where observing that a certain quantity of water overflowed, equal to the bulk of his body, he instantly saw in it the solution of the problem. Carried away by his ardor, he is said to have hastened home, without waiting to dre , crying out. "Lureka!" (I have found it!) - See SPECIFIC GRAVITY. Archime'des' Screw, or SPIRAL PUMP. n. ( Hydraul .) A machine invented by Arch i me des, the celebrated Syracusan philosopher, while studying in Egypt. Observing the difficulty of raising water from the Nile to places above the reach of the flood-tides, he is said to have designed this screw as a means of overcoming the obstacle. It consists of a pipe twisted in a spiral form round a cylinder, which, when at work, is supported in an inclined position. The lower end of the pipe is immersed in water, and when the cylinder is made to revolve on its own axis, the water is raised from bend to bend in the spiral pipe until it flows out at the top. The A. is still Fig . 180.-DOUBLE-THREADED A. SCREW. used in Holland for raising water, and draining low grounds. The Dutch water-screws are mostly of large size, and are moved by the wind, one windmill furnishing sufficient motive-power to keep several screws going at once. Arch'ing, p . a . Curved as an arch. Archiog/rapher, n. [Gr. archos , chief, and grapho , to write. The head-secretary. Archipelag'ic, a. Relating to an archipelago. Archipelago, n. A term applied to such tracts of sea as are interspersed with many islands. It is more especially applied to the numerous islands of the Ægean Sea, or that part of the Mediterranean lying between Asia Minor and Greece. These islands are principally divided into two groups called the Cyclades and Sporades . The former contains the islands of Kyth nos, Lyra, Seriphos, Keos, Anoros, Tenos, Naxos. Thera, Ios, Melos, Kimolos, ., all belonging to Greece, and forming the prov. of the Cyclades , containing an aggregate population of 120,037. The Sporades group consists of Scio, Cos, Rhodes, Samos, Mitylene, Lemnos, ., and belong to the Turkish empire, forming the sandjak or government of Djezairi-Bahri. The islands of both groups will be severally described in their proper places. Archipelago (Eastern), INDIAN, OF MALAY. This great A. contains a vast number of islands within the tropics, and extends between 95° and 135° E. Lon.; and 115 S. and 19° N. Lat., having on the N. and N.W. the Chinese sea; N.E. and E. the Pacific: and S. and S.W. the Indian ocean. It has been separated into 5 divisions, each distinguished by peculiarities of situation, climate, and productions; viz.: 1st div ., Long. 95° to 116°, includes Sumatra, Java, Bali, Lombok, Madura, Banca, Bill it on, the Malayan peninsula, and the W. or larger portion of Borneo. - 2d div ., Long. 124° to 130°, includes Celebes, Sambawa, Flores, Sandal-wood island, Timor, and the E. part of Borneo to 3o N. Lat.-3d div . , Long. 1.4° to 130°, Lat. 10° S. to 2o N., includes Ceram, Gillolo, the Papuans, Aru islands, .- 4th div ., Long. 116° to 125°; and Lat. 4° to 10° N., includes Mindanao, the Sooloos, Palawan, and N.E. part of Borneo. - 5th and last div . includes the remainder of the Philippines, and is the only portion within the limit of the hurricanes. See BANCA, BORNEO, CELEBES, JAVA, SUMATRA, PHILIPPINES, .- The other archipelagos will receive separate notice, each under its proper name. Architect. n. [Fr. architecte , from Lat. architect us; Gr. architekton, from teucho , to prepare, to make, to work.] One skilled in the art of building; one who plans or designs buildings, ., and superintends their erection; a contriver.