WHAT MAKES THUNDER?

Matamata Record, Volume VI, Issue 483, 25 October 1923, Page 4

WHAT MAKES THUNDER?

SAID TO BE ELECTRICAL. (By A Meteorological Expert.) One ol' Llie myslcrlos of sucn thunderstorms as have occurred in Great Britain during the last forty eight hours '.s the relative smallnesfr o.' the (laau'i'c done in proportion I.'* the terrific character of the forces .'operating. The impression produced yesterday morning, for instance, by some of the discharges was that of the firing of a very heavy gun—l2tn. or 15in. There was Me same concussion in the atmosphere; the saint, cracking, rushing noise, and the same kind of report. Yet actually the power exerted by a single Hash is enormously greater than that of any human gun yol made. Measurements recently carried out by Mr. C. E. Wil.'Cti at Cambridge, not without considerable - risk to himself, show that the power 1 exerted in a flash is usuaHy aboui 2,000,000 ft. tons, which would suffice to-raise a weight of 2,000 tons I,oooft. in the air Tho powor rf thft British lsi;. i.aval gu>i is 82.::00ft. tons, or less than one-twentieth of that developed by the lightning discharge The modern view of the thundercloud "is that it is an electrical generator, by which electrical currents are maintained between the earth (itself a powerful electric; machine generating or currying stupendous charges) and the conducting layer of tho upper atmosphere. The upper atmosphere appears to be markedly affected when a thunderstorm is in progress below it. Cathode rays, positive rays and X-rays seem to lip freely generated The curious continual dickering of steely -.blue to green and lilac light, which' aeeo.m'lai.ies very bad thunderstorms, may be cine to those rays in the upper atmosphere, which is also ib s region whore auroras show their marvellous colours.

j Thi- safest place in a thunder storm is Inside a Jiouse or a building. I In London, lightning conductors are not usually lilted except to very high structures, because of the : large degree to protection given by high chimneys, spires, and the mass ot wires, all of which contribute to intercept the electrical force and send it, harmlessly to the ground. But it ! is always wise in a heavy thunderi storm to got under shelter; the statisI tics proving thai in a year only .one person in a million is struck in this country do not apply to those out of doors. Trees—if they, are not isolated trees—are safer'than in the I open, but an isolated tree is the most dangerous shelter of all. . ! The distance of a storm or of the i ceiiliv of discharge can be calculated j fiutclciy by counting the seconds that I irass between the flash and the report. lof thunder. If live seconds elapse. | the distance of the discharge Is a I mile: if the report is almost instanta--1 neoutdy heard, with only a second's ' Interval or less, the disturbance is :overhead.