If a very long base is taken, it becomes increasingly open to doubt whether the portions of space emitting auroral light to the observers at the two ends are the same.
Neville), and boils at about lioo C. Magnesium and its salts are diamagnetic. It burns brilliantly when heated in air or oxygen, or even in carbon dioxide, emitting a brilliant white light and leaving a residue of magnesia, MgO.
T intervals, varying from a few weeks or months to a few years, has broken out into eruption, sometimes emitting only steam, ist and scoriae, but frequently also streams of lava.
FIREFLY, a term popularly used for certain tropical American click-beetles (Pyrophorus), on account of their power of emitting light.
Wehnelt discovered that the same effect could be produced by using instead of a carbon filament a platinum wire covered with the oxides of calcium or barium, which when incandescent have the property of copiously emitting negative ions.
In the Maribios district occur several volcanic lakelets, such as that of Masaya, besides numerous infernillos, low craters or peaks still emitting sulphurous vapour and smoke, and at night often lighting up the whole land with bluish flames.
In strictness this idea is appropriate only when the source is a luminous line, emitting cylindrical waves, such as might be obtained from a luminous point with the aid of a cylindrical lens.
With the gas in excess a heavy lurid flame emitting dense volumes of smoke results, whilst if it be driven out in a sufficiently thin sheet, it burns with a flame of intense brilliancy and almost perfect whiteness, by the light of which colours can be judged as well as they can by daylight.
Two of the five compartments into which it is divided by walls of deeply striated volcanic ash are constantly emitting steam, while a new vent displaying great activity has been opened at the base of the cone on the south side.
According to Huygens's principle (see Diffraction) each aether particle, set vibrating by an incident wave, can itself act as a new centre of excitement, emitting a spherical wave; and similarly each particle on this wave itself produces wave systems. All systems which are emitted from a single source can by a suitable optical device be directed that they simultaneously influence one and the same aether particle.