The Sound of Thunder.

Te Aroha News, Volume VI, Issue 354, 27 March 1889, Page 6

The Sound of Thunder.

One of the be*t descriptions of a common natural phenomenon is that recently given by M. Him, in which he says that the sound which is known as thunder is due simply to the fact that the air traversed by,, an elecLiic spark — that is, a flash of light r ning — is suddenly l'ahed to a very high temperature, and has its, volume, moreover, considerably increased. The column of gas thus suddenly heated and expanded is sometimes several miles long*, and, as the duration of the flash js not even a millionth of a second, it follows that the noise bursts forth at once from the whole column, though for an , observer in any one place it commences where the lightning is at the least 1 dis; tance. In precise terms, according to M, Him, the beginning of the thunder-clap gives us the minimum distance of the lightning, and the length of the thunderclap gives the length of ,the column. He also remarks that when a flash of lightning strikes the ground it is not necessarily from the place struck that the first noise is heard. Again he points oufc that a bullet whistles in traversing the air, so that, we can, toaceitain extent, follow its flight, the same thing also happening with a falling meteorite just before striking the earth. The noise actually heard has been^om,pared to the sound , produced when, oiiq tears, linen. It is due really to, the fact that the air rapidly pushed on one side in. front of the projectile, whether bullet or,,meteorite, quickly rushes back to fill the vacuum left in the reax\ H ,

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