ÆTHER, a term formerly used to signify a thin subtle matter, finer than air, and completely filling the whole space of the firmament.
Various opinions have been held respecting its precise nature: by some it is supposed to be a fluid of a peculiar kind, and confined to the regions above our atmosphere; by others, a substance so subtle and penetrating, as to be intimately diffused through the air, and to insinuate itself into the pores of all other bodies. Its existence, however, has been denied by many, who assert that the air, by its tenuity and expansion, is fully sufficient for the above-mentioned purposes.
Whatever conjectures may be formed concerning the nature and properties of this subtle fluid, there is every reason to believe in the existence of a matter finer than the air itself. Sir Isaac Newton has observed, that heat is readily communicated through a vacuum, which cannot take place without the intervention of some other medium. This, being subtle enough to penetrate even through the pores of glass, may readily be conceived to be capable of pervading all other bodies, and diffusing itself through every part of space: and thus it conveys a complete idea of an æthereal fluid.
Æther is now principally considered as a chemical composition. It is a combination of vitriolic acid and spirits of wine, and is used for a variety of medical purposes. The head-ach is said to have been often cured by rubbing it on the temples; and Dr. Conyers declares, that a tea-spoon full applied to the affected jaw, and repeated till the pain ceases, is a never-failing remedy for the tooh-ach. It has also been used in cases of rheumatism, gout, and hooping-cough, with great success. In a paroxysm of suffocative asthma, and all those diseases where the organs of respiration are affected, half a tea-spoon full of vitriolic æther in a table-spoon full of water, quickly swallowed and occasionally repeated, has often produced instant relief. Even the simple evaporation of this volatile fluid, a spoonful of which may be placed at a time in a shallow vessel contiguous to the part, has frequently been found of great service, and alleviated the most distressing shortness of breath.
A combination of spirit of sea-salt with the flowers of zinc, produces the marine æther.