EFFECTS OF LIGHTNING OF TREES.

Waikato Times, Volume III, Issue 157, 10 May 1873, Page 2

EFFECTS OF LIGHTNING OF TREES.

For some years pvrt Profewor Caspar} , of Kcemgstorg, hu^ been collecting information oil the elieots of lightuuy upon trees, &c, with a view to the elucidation of the question . whether the living tissues of trees aic ignited by the electric fluid, and ako ad to the relative liability of different species to damage from lightning. In a pamphlet before us he enumerates 53 ta*es of trees anil telegraph posts shattered or more or less injured by lightning, none of which took fire Several reported instances of coinb'^tion ryuiludcd to and dismissed as untrustworthy, or as notbasjß upon actual observation, but rather attributed to the effects <f lHitmna .Seeause no other agent could be assigned. Semtheless, one or two cases of destructiou by lire of hollow tranks of Pmus sylvestns admit of little doubt, though the actual outbreak of the fire was not obseived; but no trust- 4 worthy account of a sound growning tree having been ignited by lightning has come under his notice, beveral instance* of palms, with dijf decayed leaves, and other trees wi h rotten branches, having beeu consumed by nro communicated by the electric iluul, nave beea reported m this and other journals ; but in all cases theie appeals to have been diy decayed material, as in buildings, for it to prey up'iu. The eomparatrve or absolute immunity of certain ti ecs has froqueutly and even iccently been discussed in those pa^es, and although no positive cause has been diacovuied tor the exemption, there is no doubt that some species aie almost or quite exempt fioni damage by lightning. j liut, as L'.ispary very justly remaiks, we have no data by which to estimate statements of the relative frequency or infrequency of damage to certain species in proportion to the number of indi\ iduals of ditlerent species in the sacV, districts. It is very generally supposed that the beech, biich, and maple aie never stiuck, but casts are on record, showing that they are not always spared. The following figures show the number of each species struck in 93 recent instances coining under the observation of Caspary, Colin, A. Braun.aud others:— l Populus alba, 2 Pvriw conimnnis, 3 Ulmu*, 3 Abies pectinata, 3 iintula icrrucosa, 3 Fraxmus excel&ior, 12 Puma sylves-tria (including (5 telegraph posts), 12 Abies excelsa, 11- Populus inomlifora, j 15 Quorum (probably all Q. pedunculate), and 50 Populus pyramidalis. v The great susceptibility of the oak, Italian poj^r, le , ! ha-* been variously explained by dilfererent writers, but nothing more definite bus resulted from theirapeculatioiiß thnvM that it is probably owing to their greater conducting power. | But, according to Caspary, there must be some local toatrollmg influences not yet understood; for, although the Itahaif poplar is very abundant in Prussia, only three instances of its having been struck have come to his knowkdge, whereas hi the neighbourhood of Geneva, 16 out of 20 tiues struck by lightning wero of that species. lii order to obtain a clearer insight into the action of lightning upon trees, Caspary undertoook a series of experiment* on vegetable tissues with an ordinary friction clectncul machine. But although the results throw some light, on. the subject, he was unablo to extend |his experiments I sufficiently to render them ot any practical value. From I ' tnala with the electric spark in dilfcKent directions througM j the tisanes, it appears there is a considerable diversity in tfl conducting power. Fresh!} cut lime biauohes operated uponj longitudinally, radially, and tangentially, showed the following difleronces respectively, namely, 19, 2, and 1. Dry wood of Picca rulgaris exhibited corj'Copondmg powers of 7, 2, and 1. A microscopical inveatigafcon of tho green and dry woods acted on showed the damage to be exactly the jome in both. cases. The celL of all parts of the fabric were burst and shattered, especially thoso bordering the hold made by the electric spark ; and the injury extended to as many as ten rows of cells. A great many cases of the trees and telegraph poles struck by lightning and referred to by Caspary occurred on the mam road near KooniKsberg. A telegraph line runs along the west side of the road, outside of the poplars, and about two jards distant from them ; and m the professor's opinion se\eral of the trees were not struck directly, but by the fluid conveyed by the wiruu and given oif at intervals, the damage being comparatively slight. Curiously enough the course; o: tho current down the poles -nas almost invariably to the rfght, but to tho left down the trees. J A very remarkable instance of the effects of lightning od a large spruce fir is described nnd figured in Prolesbor CsM par) 's Memoir. The ciown ot the tree was shattered auci broken off, and in its action the lightning completely drove tho resm out of the injured wood, and left it hanging on the trunk in a large charred mass iive or six feet long ; it wa* as black as pitch, sliming, light, and brittle, and MI of turpentine. — Gardeners' Chronicle*