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ATREK — AUBURN

series of hills near Sodankyla. Sometimes a Holtz machine was introduced into the wire circuit, and when worked it enhanced the effect, or even rendered it visible when previously unseen. Coloured illustrations represent the artificial phenomenon on several occasions as very prominent, and extending to a considerable height. § 38. At the Danish polar station, Godthaab, Paulsen saw on several occasions auroral sheets, which seemed to be suspended vertically like curtains and to sweep past with great velocity, travelling from magnetic south. At Paulsen’s suggestion, Lieut. Yedel of the Ryder Arctic Expedition, 1891, 1892, kept a lookout for this phenomenon, and was able on a variety of occasions to observe the declination magnet during its occurrence. According to these observations—made on an island in Scoresby Sound, 70° 27' N. lat. —the needle moved to the west as the auroral curtain approached from the south, oscillated as the curtain passed overhead, and then moved to the east as the curtain receded towards the north (Paulsen, Bull, de VAcad. Boy... .de Danemark, 1894, p. 148). Paulsen believes the phenomenon to imply the existence of an electric current directed downwards in the space occupied, or seemingly occupied, by the auroral curtain. § 39. Numerous attempts have been made to determine the height of auroral displays. Simultaneous theodolite observations Height of have frequently been made from two stations at a auroras. considerable distance apart. The calculated heights in mean latitudes have often exceeded 100 kilometres. At Godthaab the calculations of the Danish observers often put auroral arcs at heights under 10 kilometres, and occasionally under 2. From the observations at Sodankyla, Lemstrom thought it doubtful whether the objects seen from the two ends of the base were really the same. The question has been treated with great fulness of detail by Cleveland Abbe {Terrestrial Magnetism, vol. iii., 1898, pp. 5, 53, and 149); he seems disposed to doubt whether what the observer sees as aurora has an independent objective existence. § 40. The subject of lunar influence has been treated by Ekholm and Arrhenius in several papers dealing with a great mass of observations, and containing many useful references {K. Sven. Vet.Akad. Hand., Bd. 19, No. 8 ; Bd. 20, No. 6 ; Bd. 31, No. 2). In the case alike of electric potential, thunderstorms, and auroras, they find a conspicuous tropical lunar period, 27‘32 days. They conclude, however, that the synodic lunar period, 29'53 days, found

by Fritz in auroras is not real, arising simply from the fact that moonlight affects the visibility of auroras. An investigation by Polis {Met. Zeit., 1894, p. 230) seems to indicate a synodic lunar period in thunderstorms at Aachen. Investigations into thunderstorm data at Paris by Renou {Comptes Bendus, cxviii. p. 140), and into similar data at Batavia {Batavia Observations, vol. xviii. 1895) on the other hand, would indicate that if a lunar influence exists it is small. Ekholm and Arrhenius {K. Sven. Vet.-Akad. Hand., Bd. 31, No. 3) have also examined into the existence of a period of approximately twenty-six days. They decide in favour of the existence of such a period, not merely for thunderstorms and auroras, but also for magnetic storms and for the amplitude of diurnal variation of magnetic elements. The most probable value for the period is, they find, 25'929 days. The methods and conclusions of Ekholm and Arrhenius have been critically discussed by Schuster in several papers with somewhat unfavourable results. (See Magnetism, Terrestrial, § 14). Authorities.—Lord Kelvin (Sir W. Thomson). Papers on Electrostatics and Magnetism. — Georges le Cadet. Etude du champ elcctrique de V Atmosphere. Paris, Lyon, 1898. —McAoie and Henry. “ Lightning and the Electricity of the Air,” Bulletin No. 26, U.S. Department of Agriculture, Weather Bureau. Washington, 1899.—Publications of Observatories running Water-droppers, e.g., Greenwich, Magnetical and Meteorological Observations; Batavia, Observations made at the Magnetical and Meteorological Observatory at Batavia (especially vol. xviii., for 1895) ; Lisbon, Annaes do Observatorio do Infante D. Luiz.—Publications descriptive of Observations of Aurora at Stations of International Polar Year 1882-83 (Fort Rae, Godthaab, &c.), more especially the two following, descriptive also of observations of potential gradient: Observations faites au Cap Thorsden Spitzberg, tome ii. Stockholm, 1887. Expedition Polaire Finlandaise (1882-84), tome iii. Helsingfors, 1898. The following, amongst somewhat numerous, historical reviews of our knowledge of atmospheric electricity, must also be noted :—Exner. Wien. Sitzungsberichte, xciii. (Abth. ii.), 1886, p. 222.—Arrhenius. Met. Zeitschrift, 1888, p. 297 and p. 348.—Elster and Geitel. Met. Zeitschrift, 1890, p. 252, and Bull. No. 11, U.S. Weather Bureau, partii. p. 510. Washington, 1895.—Schuster. Nature, vol.Uni., 1896, p. 207.—Trabert. Met. Zeitschrift, 1898, p. 401. —Exner. Met. Zeitschrift, 1900, p. 529. /c> Ch

Atrek, a river rising in the Persian province of Horassan, enters the S.E. corner of the Caspian Sea, after a course of nearly 300 miles. In its lower course it forms the frontier between Persia and Russia.

per cent, of the population was illiterate. The land under cultivation comprised 1,383,200 acres, of which 918,840 acres were plough-land, and 41,990 acres in vines. The wheat crop in 1899 yielded a value of £1,100,281. Rye, barley, oats, and mangoldwurzel also contribute to the agricultural wealth of the department. The production of vines in 1899 amounted to the value of £300,000. In 1899 the live stock numbered 31,220 horses and 88,790 cattle. As it lacks both coal and iron, the department does little in the way of working metals, producing only cast-iron and steel to the value in 1898 of £60,000 ; but the textile industry has assumed large proportions around Troyes, where the cotton manufacture employs 24,000 looms and 70,000 spindles. Aubervilliers-Ies-Vertus, a French village in the arrondissement of St Denis, department of Seine, on the canal St Denis, 2 miles from right bank of Seine and 1 mile N. of the fortifications of Paris. Near it is a fort of the 2nd line. Manufactures include chemicals, glue, cardboard, printing ink, and glass, and there are iron-works. Population (1881), 19,340; (1891), 24,757; (1896), 27,064; (1901), 31,215.

Attleborough, a town of Bristol county in south-eastern Massachusetts, U.S.A. It has an area of 28 square miles, with a rolling surface, and contains a large rural population, with a village of considerable size, bearing the same name as the town. This has manufactures of a varied character, largely jewellery. It is on the New York, New Haven, and Hartford railway. It was incorporated in 1694. Population (1890), 7577; (1900), 11,335.

Attock, a town and fortress of British India, on the Indus, in the Rawal Pindi district of the Punjab, 47 miles by rail from Peshawar. In 1883 an iron girder bridge of five spans was opened, which carries the Northwestern railway to Peshawar, and which also has a subway for wheeled traffic and foot passengers. The military Auburn, capital of Androscoggin county, Maine, importance of Attock has diminished, but it still has a U.S.A., situated on the Androscoggin river, which furgarrison of artillery and infantry. St. Peter’s Church is nishes abundant water-power. It has communication by three railways, the Maine Central, the Grand Trunk, a fine building. Population, about 3000. and the Portland and Rumford Falls. Its manufactures Atui. See Cook Islands. consist mainly of cotton goods and boots and shoes. Aube, a department in the E. of France, watered Population (1880), 9555; (1890), 11,250; (1900), 12,951. by the Seine and its tributary the Aube. Auburn, capital of Cayuga county, New York, Area, 232/ square miles, with 26 cantons and 446 communes. U.S.A., situated in 42° 55' N. lat. and 76° 35' W. long., The population decreased from 257,374 in 1886 to 251,435 in 1896! at the outlet of Owasco lake, at an altitude of 673 feet. The chief towns are Troyes (52,000 inhabitants in 1896), Bar-surAube, Bar-sur-Seine, Nogent, Arcis, and Romilly. Births (1899), Though the site is hilly its plan is regular. The city is 4547, of which 463 were illegitimate ; deaths, 5641; marriages! divided into ten wards, has a good water-supply pumped 1693. In 1896 there were 696 schools, with 32,000 pupils. One from the lake, and most of its streets are macadamized.