LIGHTNING HOLES.

Wairarapa Daily Times, Volume VIII, Issue 2471, 8 December 1886, Page 2

LIGHTNING HOLES.

Professor Brun has published in the Arohivea de Geneva an interesting study on tlie so-called lightening holes to bo found in the High Alps., Ho andothor investigators have found them at heights of, from 3,338 to 4,000 meters, or between 11,000 and 13,000 foot ahoyo the sea level, Usually they aw found on summits. Sometimes on the .rooky mass, whiph has been vertifiod in the passage of the electric fluid, presents the appearance of scattered pearls, sometimes of a series of semispherical cavities only a few millimeters in diameter. Somotimos there are vitrified rays going out from a central point to a distance of four or five inches,- 'Sometimes a block-dotaohed (from, the mass appears as if bored through by a cannon-ball, the hollow passage being quite vetrifiod. The thickness? of this vitrified coating or stratum never oxceeds a millimetre, and is sometimes not moro than a quarter that depth." The varying colors which it prosents depend on the qualities and composition of tho rock; The same may be said as to ita transparency, On the Rungnscheom the glass thus formed by the lightening is black, owing to the quantity of actinolith whioh the rock contains. It is brown on La Ruinette, the rock consisting of feldspar, mixed with gueiss, containing chloride of iron. Under the mioroscope these lightening holes display many interior cavities, vhioh must be attributed to the presence of wator in the rock at the momont of molting by the electric discharge. This vitrified material has no influonce on polarised light,