Page:The New International Encyclopædia 1st ed. v. 01.djvu/116

into blossom by the last of May and continues to bloom without cessation for four or five months. The corolla tube is cylindrical and the limbs are spreading. The blossoms are red, blue and white, with all intermediate shades.

ACHIN, a-ehen', or ATCHEEN. A petty kingdom of about 20,000 square miles area, with more than half a million inhabitants, at the north end of Sumatra, famed from ancient times as- part of the Golden Chersonese. The country is mountainous and intersected with many rivers The famous Gold Mountain, 6000 feet high, is at the extreme northern point, with the capital city of Achin at its base.

The shorter stature, darker color, etc., of the aborigines of Achin has led some authorities to separate them from the Sumatrans in general, and their language is by others held to be Poly- nesian rather than Malay at bottom. While un- doubtedly Malays, the Achinese, like several other peoples of the East Indies, may have a strain of Arab blood. In the seventh century the Hindu missionaries introduced civilization, and many enii.'rants from India settled here. In the thirteenth century the people were converted to the faith of Islam, the sultans of Achin claiming descent from the first Mohammedan missionary. When in the sixteenth century Europeans reached Achin, they found astonishing wealth. The Ach- inese sent an embassy to the powerful Dutch republic, and the envoys had audience of Prince Maurice in his camp before Grave in 1602. The Dutch kept up intermittent trade intercourse with them until 1811. when Sumatra was ceded to the British. When the Dutch regained nom- inal possession. Great Britain stipulated that none but British citizens should reside in Achin, and that the Dutch should not conquer the little kingdom, the English wishing to retain the com- merce. The piratical instincts of the Achinese, however, led them into conflicts with the Dutch, who found it necessary to chastise them. In 1871, by the Hague Treaty, the British withdrew their reservation, and the Dutch sent an expedi- tion in 1873 to capture the chief city and invade the country. They were beaten in this, as well as in other expeditions, and the country was not pacified until several years later, when a civil government was instituted. The Achin wars have cost the Netherlands 12,000 lives and nearly one hundred million dollars for blockade and naval and military operations, and the country is yet practically unsubdued in the interior. This is not merely owing to the fanatical spirit of independence in the natives, but also and more because Achin furnishes a rich and tempting field for British blockade runners. There was an outbreak in 1901. There are numerous works in Dutch treating of Achin, and there are in Hol- land many monuments and trophies of the war. Besides the historical work of Veth, Atchin (Leyden, 1873), the standard treatise on the Achinese is Snouck, De Ajehers (two volumes, Batavia, 1893-95).

ACHMET, aK'iuet. See Ahmed.

ACHMET, iiK'mgt, or AHMED, iiii'med. The name of three sultans of Turkey, of whom Achmet III. (reigned 1703-30) was the most famous. It was this sovereign who sheltered Charles XII. after his defeat at Pultowa in 1709. He wrested the Morea from the Venetians in 1715. Having invaded Hungary, he was defeated by Prince Eugene at Peterwardein in 1716, and

later near Belgrade, and compelled to cede to Austria, by the treaty of Passarovitz, 1718, Belgrade, the Banat, and other territories. The soldiers drove him from the throne in 1730, and he died in prison in 1736.

A'CHOR. A valley which forms the north- ern boundary of Judah (Joshua xv: 7) near Jericho. Its identification is uncertain, though Wady-el-Kelt has been suggested, which, how- ever, is not broad enough to become "a place for the herds to lie down in" (Isaiah lxv : 10).

ACHO'RION. See Favus.

ACHRAS, fik'ras, See Black Bully.

ACHROMATIC, ak'ru-mat'ik. See Telescope.

ACHRO'MATISM a priv. + xpi-if'tt, colorlessness, from Gk. a a priv. + .i/-,-. chroma, color). The property by virtue of which certain combinations of lenses and prisms refract a beam of white light without producing dispersion of certain colors (See Dispersion.) Newton, misled by imperfect experiments, concluded that dispersion could not be annulled without annulling refraction. Hall, in 1733 and later, Dollond (independently), found that certain media have large powers of refraction with small dispersion, while others give small refraction with large dispersion; so that the dispersion of two colors produced by one medium can be corrected by that due to another, while the deviation of the light from its original direction is not entirely annulled. For example, by properly combining a convex lens of crown-glass with a concave one of flint-glass an "achromatic lens" can be produced which will have the same focus for the two selected colors, while the foci for the other colors are at neighboring points along the axis of the lens. It is thus seen that the achromatism in the above arrangement is not perfect. In Fig. 1 a beam of white light having the direction c d meets the crown-glass prism and is refracted. Dispersion also takes place, and the beam as it emerges is separated into its component colors. Adjacent to the prism of crown-glass is one of flint-glass, whose action is to bring together the rays so that they emerge parallel, with the desired deviation. The reason is that prisms of different media do not give exactly similar spectra, the colors being dispersed according to different laws for different media. Fig 2. shows achromatic combinations combinations of lenses where the flint and crown glasses are combined with the same effect as in the achromatic prism illustrated. A combination of three lenses, or prisms, gives a better approximation to absolute achromatism than a combination of two.

Fig. 1. ACHROMATIC PRISM.

Fig. 2. ACHROMATIC LENSES.

If a lens is to be used for visual observations, it is "corrected" generally for a definite wave-length in the yellow and one in the