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 most picturesque is Mustapha Supérieur, about 2 m. from the centre of the city on the slopes of the hills to the south. Here are the summer palace of the governor-general, many fine Moorish and French villas and luxurious hotels, all surrounded by beautiful gardens. A numerous British colony resides at Mustapha, where there is an English club. Mustapha Inferieur is built on the lower slopes of the hills. Farther to the south is the large Jardin d’Essai, containing five avenues of palms, planes, bamboos and magnolias. Notre-Dame d’Afrique, a church built (1858–1872) in a mixture of the Roman and Byzantine styles, is conspicuously situated, overlooking the sea, on the shoulder of the Bu Zarea hills, 2 m. to the north of the city. Above the altar is a statue of the Virgin depicted as a black woman. The church also contains a solid silver statue of the archangel Michael, belonging to the confraternity of Neapolitan fishermen. Beyond Notre-Dame d’Afrique is the beautiful Valley of the Consuls, very little changed since the time of the deys. (The valley was in those days the favourite residence of the consuls.) At the Petit Séminaire, on the site of the old French consulate, Cardinal Lavigerie died (1892).

In 1906 the population of the commune of Algiers was 154,049; the population municipale, which excludes the garrison, prisoners, &c., was 145,280. Of this total 138,240 were living in the city proper or in Mustapha. Of the inhabitants 105,908 were Europeans. French residents numbered 50,996, naturalized Frenchmen 23,305, Spaniards 12,354, Italians 7368, Maltese 865, and other Europeans (chiefly British and Germans) 1652, besides 12,490 Jews. The remainder of the population—all Mahommedans—are Moors, Arabs, Berbers, Negroes, with a few Turks. The vast majority of the Europeans are Roman Catholics. Most of the naturalized French citizens are of Spanish or Italian origin.

History.—In Roman times a small town called Icosium existed on what is now the marine quarter of the city. The rue de la Marine follows the lines of a Roman street. Roman cemeteries existed near the rues Bab-el-Oued and Bab Azoun. Bishops of Icosium—which was created a Latin city by Vespasian—are mentioned as late as the 5th century. The present city was founded in 944 by Bulukkin b. Zeiri, the founder of, the Zeirid-Sanhaja dynasty, which was overthrown by Roger II. of Sicily in 1148 (see .) The Zeirids had before that date lost Algiers, which in 1159 was occupied by the Almohades, and in the 13th century came under the dominion of the Abd-el-Wahid, sultans of Tlemçen. Nominally part of the sultanate of Tlemçen, Algiers had a large measure of independence under amirs of its own, Oran being the chief seaport of the Abd-el-Wahid. The islet in front of the harbour, subsequently known as the Penon, had been occupied by the Spaniards as early as 1302. Thereafter a considerable trade grew up between Algiers and Spain. Algiers, however, continued of comparatively little importance until after the expulsion from Spain of the Moors, many of whom sought an asylum in the city. In 1510, following their occupation of Oran and other towns on the coast of Africa, the Spaniards fortified the Penon. In 1516 the amir of Algiers, Selim b. Teumi, invited the brothers Arouj and Khair-ed-Din (Barbarossa) to expel the Spaniards. Arouj came to Algiers, caused Selim to be assassinated, and seized the town. Khair-ed-Din, succeeding Arouj, drove the Spaniards from the Penon (1530) and was the founder of the pashalik, afterwards deylik, of Algeria. Algiers from this time became the chief seat of the Barbary pirates. In October 1541 the emperor Charles V. sought to capture the city, but a storm destroyed a great number of his ships, and his army of some 30,000, chiefly Spaniards, was defeated by the Algerians under their pasha, Hassan. Repeated attempts were made by various European nations to subdue the pirates, and in 1816 the city was bombarded by a British squadron under Lord Exmouth, assisted by Dutch men-of-war, and the corsair fleet burned. The piracy of the Algerians was renewed and continued until 1830. On the 4th of July in that year a French army under General de Bourmont attacked the city, which capitulated on the following day (see, History.)

ALGOA BAY, a wide, shallow bay of South Africa, 436 m. E. from the Cape of Good Hope, bounded W. by Cape Recife, E. by Cape Padrone. St Croix Island in the bay is in 33° 47′ S. 25° 46′ E. On this island Bartholomew Diaz made his second landing in South Africa some time after the 3rd of February 1488, and from the cross which he is thought to have erected on it the island gets its name. Algoa Bay was the first landing-place of the British emigrants to the eastern province of Cape Colony in 1820. At a spot 6 m. N.E. of Cape Recife these emigrants founded a town, (q.v.), its harbour being sheltered from all winds save the S.E. By seafarers “Algoa Bay” is used as synonymous with Port Elizabeth.

ALGOL, the Arabic name (signifying “the Demon”) of Persei, a star of the second magnitude, noticed by G. Montanari in 1669 to fluctuate in brightness. John Goodricke established in 1782 the periodicity of its change in about 2d 21h and suggested their cause in recurring eclipses by a large dark satellite. Their intermittent character prompted the supposition. The light of Algol remains constant during close upon 56 hours; then declines in 6 hours (approximately) to nearly one-fourth its normal amount, and is restored by sensibly the same gradations. The amplitude of the phase is 1·1 magnitude; and the absence of any stationary interval at minimum proves the eclipse to be partial, not annular. Its conditions were investigated from photometric data, by Professor E. C. Pickering in 1880; and their realization was finally demonstrated by Dr H. C. Vogel’s spectroscopic measures in 1889. Previously to each obscuration, the star was found to be moving rapidly away from the earth; its velocity then diminished to zero pari passu with the loss of light, and reversed its direction during the process of recovery. Algol, in fact, travels at the rate of 26·3 miles a second round the centre of gravity of the system which it forms with an invisible companion, while the two together approach the sun with an unvarying speed of 2·3 miles per second. The elements of this disparate pair, calculated by Dr Vogel on the somewhat precarious assumption that its dark and bright members are of equal mean density, are as follows:—

The plane of the joint orbit, in which no deviation from circularity has yet been detected, nearly coincides with the line of sight. The period of Algol, as measured by its eclipses, is subject to complex irregularities. It shortened fitfully by eight seconds between 1790 and 1879; soon afterwards, restoration set in, and its exact length in 1903 was 2d 20h 48m 56s, being only two seconds short of its original value. By an exhaustive discussion, Dr S. Chandler ascertained in 1888 the compensatory nature of these disturbances; and he afterwards found the most important among several which probably conspire to produce the observed effects, to be comprised in a period of 15,000 light-cycles, equivalent to 118 years. An explanatory hypothesis, propounded by him in 1892, is still on its trial. The system of Algol, according to this view, is triple; it includes a large, obscure primary, round which the eclipsing pair revolves in an orbit somewhat smaller than that of Uranus, very slightly elliptical, and inclined 20° to the line of sight, the periodic time being 118 years. The alternate delay and acceleration of the eclipses are then merely apparent; they represent the changes in the length of the light-journey as the stars perform their wide circuit. If these suppositions have a basis of reality, the proper motion of Algol should be disturbed by a small, but measurable undulation, corresponding to the projection of its orbit upon the sky; and although certainty on the point cannot be attained for some years to come, Lewis Boss regarded the evidence available in 1895 as tending to confirm Dr Chandler’s theory.