Page:The American Cyclopædia (1879) Volume I.djvu/75

 ACARNANIA ACCELERATION 55 harbors on the W. coast, and during the Span- ish dominion in Mexico was the focus of the trade from China and the East Indies, and a place of considerable importance. It has since relapsed into insignificance, although previous to the opening of the Pacific railroad the Cali- fornia trade imbued it with a transitory com- mercial life, in consequence of its having been made the coaling station for the steamers be- tween Panama and San Francisco. ACARNANIA, a province of ancient Greece, bounded N. by the Ambracian gulf and Am- philochia, which is by some included in Acar- nania, E. by ^Etolia, and S. W. and W. by the Ionian sea. It 'is mountainous, with nu- merous lakes and tracts of pasture, and its hills are still well wooded. Among its earliest inhabitants were Leleges, Curetes, and colo- nists from Argos. The Acarnanians were more akin in character and manners to their savage neighbors of Epirus than to the Greeks proper. Up to the time of the Peloponnesian war they were a race of shepherds, continually fighting, but faithful and steadfast. They also figure as pirates. Though possessing several good har- bors, the Acarnanians paid little attention to commercial pursuits. At the present day it forms with ^Etolia a nomarchy or province of the kingdom of Greece; area, 3,024 sq. m. ; pop. in 1870, 121,693. The country is thin- ly inhabited, and little cultivated, notwith- standing its fertile soil and treasures of sul- phur and coal. Besides the Greek popula- tion, there are bands of nomadic Kutzo-Wal- lachs, here called Karagunis (black cloaks), who in the winter descend from the north- ern mountains of Agraphi and encamp with their herds at the edge of the woods. They speak a dialect akin to the Latin. Different from them are the nomadic Sarakatzanes, who are of Greek origin. A band of the Karagunis embrace's from 50 to 100 families, constituting a stani, and is commanded by the most wealthy member as chief (tchelinga), who farms the pastures and fixes the time of departure. They are skilled in making cotton goods. Capital, Missolonghi. ACARl'S, the name of a genus of insects, commonly called mites. They belong to the spider family. They are all extremely minute, and mostly microscopic insects. Some are parasitic, as the itch insect, acarus scabiei. The different species infest brown sugars, meal, cheese, &c. To collections of insects and stuffed birds they do much injury. Cam- phor tends to keep them off, and corrosive sublimate is a still more effectual protection. (See EPIZOA, and ITCH.) ACASTUS, in mythology, son of Pelias, king of lolcus. He took part in the Calydonian hunt and the expedition of the Argonauts. He revenged the murder of his father, in which his sisters were the instruments of Medea, by driving Jason and Medea out of lolcus, and instituted funeral games in honor of Pelias. A CCA I), one of the four cities in the "land of Shinar " or Baby Ionia, which, according to Gen. x. 10, were the beginning of Nimrod's king- dom. Among other places, it has been iden- tified with Nisibis. Rawlinson sees in Accad the name of " the great primitive Hainite race " in Babylonia. ACCELERATION, an increase in velocity of a moving body, either constant and uniform or variable. When the velocity receives equal increments in equal times, it is uniform. This is the case with bodies falling in a vacuum, the increase of which is in every second about 32^- feet, but varies with the latitude of the place and the height above the ocean, or the depth under the surface of the earth. As gravitation is the cause of this acceleration, scientists have accepted the letter g for it as a symbol, meaning 31 or 32 or any other number of feet, as the case may be. At the distance of the moon the acceleration is 3,600 times smaller, and g is thus equal to about 4- inch ; while at the surface of the sun and large planets it is much greater by reason of the greater attraction of large masses. Acceleration is variable when its velocity increases at one instant in a greater or lesser ratio than in an- other. This is the case with a body falling from a great height toward the earth through the air ; the resistance of the latter increasing with the velocity, the ratio of increase must diminish till the accelerating force, that is, gravitation (<7), balances the resistance of the air, when the body will continue to fall with uniform motion, which motion may then be- come retarded if the body in its downward course enters strata of air of greater density and thus at greater resistance. The motions of the planets, and especially of the comets, in their orbits around the sun, offer other illus- trations of variable acceleration. Acceleration of the Moon. Halley noticed that the compar- ison of ancient eclipses with modern shows that the moon moves faster now than formerly, and the solution of the problem as to the cause of this acceleration was first given by Laplace, who showed that the slow diminution of the eccentricity of the earth's orbit must produce an acceleration of the moon's motion and a decrease in the period of its revolution. Adams has recently shown that Laplace over- estimated the effect of the change of the earth's orbit on the moon by one half, and that his demonstration therefore only accounts for half of the moon's acceleration. The cause of the other half remains to be found out. De- launy ascribes it to a retardation in the earth's motion of rotation by the influence of the tidal wave raised by the moon, and reacting on the latter. The earth's daily rotation, however, ap- pears to undergo neither acceleration nor re- tardation; therefore others ascribe it to a resisting medium, filling the interplanetary space and revolving round the sun with the planets, and which thus only can affect their moons, which at every half revolution move