Auro´ra Borea´lis, a luminous meteoric phenomenon appearing in the north, most frequently in high latitudes, the corresponding phenomenon in the southern hemisphere being called Aurora Australis, and both being also called Polar Light, Streamers, &c. The northern aurora has been far the most observed and studied. It usually manifests itself by streams of light ascending towards the zenith from a dusky line of cloud or haze a few degrees above the horizon, and stretching from the north towards the west and east, so as to form an arc with its ends on the horizon, and its different parts and rays are constantly in motion. Sometimes it appears in detached places; at other times it almost covers the whole sky. It assumes many shapes and a variety of colours, from a pale red or yellow to a deep red or blood colour; and in far northern latitudes serves to illuminate the earth and cheer the gloom of the long winter nights. The appearance of the aurora borealis so exactly resembles the effects of experimental electrical phenomena that there is every reason to believe that their causes are similar. When electricity passes through rarefied air it exhibits a diffused luminous stream which has all the characteristic appearances of the aurora, and hence it is highly probable that this natural phenomenon is occasioned by the passage of electricity through the upper regions of the atmosphere. The synchronism of auroral display with disturbances of the magnetic needle is an ascertained fact, and the connection between auroræ and magnetism is further evident from the fact that the beams or coruscations
issuing from a point in the horizon west of north are frequently observed to run in the magnetic meridian. What are known as magnetic storms are invariably connected with exhibitions of the aurora, and with spontaneous galvanic currents in the ordinary telegraph wires; and this connection is found to be so certain that, upon remarking the display of one of the three classes of phenomena, we can at once assert that the other two are also present. In recent years it has been established that auroræ wax and wane in frequency pari passu with sun-spots in an 11-year cycle, and that they often manifest themselves about the time of transit of a conspicuous spot across the sun's central meridian. Also they frequently recur at successive intervals of about 27 days, which is the period of a solar rotation relative to the earth. It is therefore inferred that auroræ are largely excited by influences proceeding from the sun, and it is suggested that they are the result of the impinging upon our upper atmosphere of streams of electric corpuscles expelled from the solar orb, these streams when approaching our planet being mainly directed to its higher latitudes as a consequence of its magnetic polarity. The aurora borealis is said to be frequently accompanied by sound, which is variously described as resembling the rustling of pieces of silk against each other, or the sound of wind against the flame of a candle. The aurora of the southern hemisphere is quite a similar phenomenon to that of the north.—Bibliography: A. Angot, Les Aurores Polaires; Captain H. P. Dawson, Observations of the International Polar Expeditions, 1882-3, Fort Rae.
Aurungabad. See Aurangabad.
Aurungzebe. See Aurangzib.
Ausculta´tion, a method of distinguishing the state of the internal parts of the body, particularly of the thorax and abdomen, by observing the sounds arising in the part either through the immediate application of the ear to its surface (immediate auscultation), or by applying the stethoscope to the part, and listening through it (mediate auscultation). Auscultation may be used with more or less advantage in all cases where morbid sounds are produced, but its general applications are: the auscultation of respiration, the auscultation of the voice; auscultation of coughs; auscultation of sounds foreign to all these, but sometimes accompanying them; auscultation of the actions of the heart; obstetric auscultation. The parts when struck also give different sounds in health and disease.
Auso´nia, an ancient poetical name of Italy.
Auso´nius, Decimus Magnus (c. A.D. 310-395), Roman poet, born at Burdigala (Bordeaux). Valentinian entrusted to him the education of his son Gratian, and appointed him afterwards quæstor and pretorian prefect. Gratian appointed him consul in Gaul, and after this emperor's death he lived upon an estate at Bordeaux, devoted to literary pursuits. He wrote epigrams, idyls, eclogues, letters in verse, &c., still extant, and was probably a Christian. He was rather a man of letters than a poet, and his poems are devoid of inspiration.
Aus´pices, among the ancient Romans strictly omens or auguries derived from birds, though the term was also used in a wider sense. Nothing of importance was done without taking the auspices, which, however, simply showed whether the enterprise was likely to result successfully or not, without supplying any further information. Magistrates possessed the right of taking the auspices, in which they were usually assisted by an augur. Before a war or campaign a Roman general always took the auspices, and hence the operations were said to be carried out 'under his auspices'. See Augur.
Aus´sig, a town in Bohemia, in the republic of Czecho-Slovakia, formerly in Austria, near the junction of the Bila with the Elbe, 42 miles N.N.W. of Prague; has large manufactures of woollens, chemicals, &c. The town is now known as Ousti nad Labem. Pop. 40,000.
Aus´ten, Jane, English novelist, born 1775, at Steventon, in Hants, of which parish her father was rector. Her principal novels are, Sense and Sensibility; Pride and Prejudice, which Disraeli is said to have read seventeen times; Mansfield Park; and Emma. Two more were published after her death, entitled Northanger Abbey and Persuasion, which were, however, her most early attempts. Her novels are marked by ease, humour, and a complete knowledge of the domestic life of the English middle classes of her time. She died in 1817.