A remarkable connection has been observed between the aurora and the earth’s magnetism, the magnetic needle showing great disturbance during a display of the aurora. The arches of the aurora most commonly traverse the sky at right angles to the magnetic meridian, though deviations from this direction are not rare. Sir J. Franklin found that the disturbance of the needle was not always proportionate to the agitation of the aurora, but was always greater when the quick motion and vivid light were observed to take place in a hazy atmosphere. The aurora is most frequent and vivid in high latitudes, towards either pole, but the meteor is not confined to these parts, as Dr Hooker states that one of the most brilliant displays he ever witnessed was under the tropical sky of India; and other observers have recorded instances of its appearance in the equatorial districts of the globe.
The attitude of the aurora varies considerably; there appears to be little doubt, however, that it frequently occurs at small elevations. Both Franklin and Parry record instances where it appeared below the level of the clouds, which they describe as having been hidden behind the masses of its light, and as reappearing when the meteor vanished. It would seem that there are two distinct kinds of aurora one dependent upon local causes, as in the cases last given, while in the other causes are probably cosmical, and the auroral effects are seen at very distant points of the earth’s surface.
AURORA POMADE. For promoting the action of the skin. Cocoa butter with orris.
AUTOG′ENOUS (tŏj′-). Syn. Autoge′′neal; Autog′enus (tŏj′). L. Self-generating or affecting; acting without the aid of foreign matter. In anatomy, &c., developed from distinct and independent centres; as parts or processes. Among metallists, it denotes a method of joining metals by fusing the parts in contact, by means of a flame of hydrogen, or of a mixture of hydrogen and common air, without the intervention of a fusible alloy or solder. Lead, and even ordinary hard solders, are, however, sometimes so employed, and the name, though improperly, retained.
AUTOMAT′IC. Syn. Automati′cus, Autom′atus, L.; Automatique, Fr.; Automatische, Ger. Self-acting or self-moving, or that seems to be so; mechanical; of or resembling an automaton. In physiology, involuntary, applied to functions which are performed without the operation of the will; as the movements in respiration, the contractions and dilations of the heart, the persistent contraction of the sphincters, &c. In mechanics, &c., moving and acting from concealed machinery; also, as applied to machinery, self-regulating and directing, within the limits prescribed by its author, though moved by external power. To the last class belongs the self-acting machinery of our flax and cotton mills, our engineering establishments, &c.; in which the elemental powers are made to animate, as it were, millions of complex organs, infusing into forms of wood, iron, and brass, an agency resembling that of intelligent beings.
The manufactures in which such machinery is employed are termed the AUTOMATIC ARTS.
AUTOPSY. Literally, personal observation or examination; ocular view. The term, however, is now applied, rather loosely, to a post-mortem investigation. A post-mortem may be performed with the object of endeavouring to ascertain the cause of death in a medico-legal inquiry, or in the furtherance of the study of pathology. It is also a preliminary to embalmment, and is sometimes had recourse to as a means of saving the child when a woman dies in full pregnancy.
In France no post-mortem examination is permitted to take place until at least 24 hours after death, this delay being enforced as a safeguard against the possibility of the body operated upon being still alive. In England no post-mortem can be made without the consent of the friends of the deceased, unless by warrant from a coroner; although in many public institutions this consent is dispensed with. Whenever, however, a prisoner dies in gaol an inquest and post-mortem are held on the body.
An autopsy is to be discouraged in cases where a person has died from infectious disease; but should the law require it to be undertaken, disinfectants both during and after the operation should be liberally had recourse to.
AUTUMNAL FEVER. This term is chiefly employed by American medical writers to designate typhoid fever, because of its prevalence in the autumn.