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Show THE SOUND OF THUNDER. How to Ascertain How Fur Away tl Thunder I. One of the most terse and succinct descriptions of a natural phenomenon is that recently given by M. Ilirn, in which he says that the sound which is known as thunder is due simply' to the fact that the air traversed by an electric elec-tric spark, that is, a flash of lightning, is suddenly raised to a very high temperature tem-perature and has its volume, moreover, considerably increased. The column of gas thus suddenly heated and expanded ex-panded is sometimes several miles long and, as tho duration of the Hash is not over the millionth of a second, it follows that the noise bursts forth at once from the whole column, though, for an observer at any one place, it commences where the lightning flash is at the least distance. In precise terms, the beginning of tho thunderclap thunder-clap gives tho minimum distance of the lightning, and the duration of the rolling of tho thunder the length of the column of heated air. Prof. Ilirn also remarks that when a flash of lightning light-ning strikes the ground, it is not necessarily ne-cessarily from the placo struck that the first noi.-o is heard. Again he points out that a bullet whistles in traversing the air. so that we can, to a certain extent, follow its flight. The same thing also happens with a falling meteorite just before striking the earth. Tho noise actually heard has been compared to tho sound produced when one tears linen, it is duo. really, to tho fact that tho air rapidly pushed on one sido of the piojectile in front, whether bullet or meteorite, quickly rushes back to 1111 tho gap left in the rear. |