LIGHTNING.

Hawera Star, Volume XLV, 19 January 1926, Page 3

LIGHTNING.

DANGER OF TREE SHELTER.

INTERESTING INVESTIGATIONS

The death of two telegraph linesmen and the injuries and shock sustained oy four, others who were .sheltering under a large tree during a violent thunderstorm in the Kangaroo Valley recently is a striking example of the danger that attaches to sheltering under arge trees in open country during electrical storms (says the Sydney Morning Herald). Accidents of this kind are reported fairly frequently in Australia, and so often are trees struck by lightning that thev are coming to be regarded as very unreliable shelters from the heavy ram showers which accompany thunderstorms. Ju the recent fatality the linesmen had descended from work on the telegraph wires to take shelter under a large tree, and a "flash struck the tree, throwing all six to the ground, and killing two of the unfortunate men instantly. It is common for great trees to I>q riven as though struck from above with a great axe;- and on such occasions, apart from the danger of flying timber, real danger attaches, to being in the immediate vicinity owing to electrical discharges given off by the tre e itself, similar to those that have occurred at times from lightning conductors. ' Thunderstorms and the many phenomena. of atmospheric electricity have been a subject of investigation for many years, and it was established very early that when an electrically-charged cloud passed near another stratum of cloud or over a hilltop, trees, tower, or other outstanding prominence, a discharge takes place from the cloud in the form of lightning. Heavv rain is an effective aid in the quiet discharge of lightning, and frequently lightning ceases with rain. Trees, particularly in open country, become, -therefore, an attraction to lightning; but the only other option afforded in many cases—namely, that of standing out in the open during the heavy showers —is not always a. safe one. " When the option afforded is betwen sheltering in a house or under a tree, the house is undoubtedly the safer choice; but when th e option is between standing in the open or under the tree, the safer course is not s® clear. Statistics bear this out. In Hungary during the three years 1901-3 15 per cent, of the total , deaths by. lightning occurred under trees as against 57 per cent, wholly in the open. In the United States during 1900 only 10 per cent, of the- deaths by lightning where precise conditions were ascertained occurred under trees, compared 'with! 52 per cent, in the open. If the risk under trees were greater than that in the open, the only comment on these figures must be that at least five or six times the. number of people who take shelter under trees must remain in the open, which is scarcely what might be expected in practice. A remarkab’e fact, which has been proved by many investigations, is that certain species of trees are more liable to be struck than others, but so far as is known this research has not been applied to Australian trees, either as between different Australian species or in comparison with European and Einglish trees. An isolated tree occupying an exposed position, is,.' of course, more likely to be struck than the average tree in a wood, but data collected in Germany over a period of years indicated that the liability to lightning on a similar number of trees of different Species was oak 57, fir 39. pine 5, and observations showed that the order of liability to lightning was oak. poplar, and pear trees respectively, whi 1 © beech trees were regarded as exceptionally safe, blit these investigations are not conclusive, as questions of height, exposure. or proximity to water may, uartlv account for one tree being struck in preference to others. Soil is also another important factor, and observations in Germany have shown that the liability to lightning stroke may b© placed'at chalk 1, clay 7, sand 9, and loam 22.