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♦ KNOWLEDGE ♦ 



[AcGiST 1, 1889. 



graph of the boots worn by some children who were struck by 

 lightning in Atcham Church, near Shrewsbury, in July, 1879. 

 Sometimes the body of a person struck by lightning has 

 markings on it of an arborescent or treelike character. A 

 very interesting photograph of such markings on the arm 

 of a boy wlio was struck by lightning at Duns, Berwick- 

 shire, was obtained in June 1883. The boy, who was 

 thirteen yeai-s of age, had sought shelter with three other 

 boys in a stable when the occurrence took place ; he was 

 thrown to the ground and hurt about the face and forehead 

 by the fall. His father, who is a chemist, writes : — 



" The motion of the arms was for some while completely 

 paralysed, inasmuch as he was unable vmtil some consider- 

 able time after regaining consciousness to remove his hands 

 from his pockets, where he had placed them before the acciilent. 

 There was also in the arms a sensation of numbness and 

 cold, and he fancied that they had been broken at the 

 elbows. Other voluntary movements were at first inac- 

 curate and unsteady. Later, upon his complaining of a 

 burning heat in the arms his coat was removed, and mark- 

 ings of an arborescent character were discovered stretching 

 from below the left elbow to the shoulder, and throwing 

 branches of a less complicated character across the left 

 chest. The marks were of a ramified, tree-like form, and 

 seemed to radiate from two centres, as if the lightning had 

 first struck the arm in two places, and had thence broken 

 over the surrounding skin. Shortly after the accident the 

 boy walked home without assistance, and on his arrival the 

 marks were subjected to a closer inspection. They proved 

 of a red colour, somewhat similai- in shade to that of the 

 spots of measles or scarlet fever. The sm-face of the skin 

 was slightly raised over them, and the superficial heat of 

 the injured arm was greater than that of the rest of the 

 body. For two hoiu-s after the stroke they retained theii- 

 original appearance, remaining to the naked eye at least 

 perfectly unaltered. By 7.30 p.m., eight and a half hours 

 after the accident, they were hardly visible, and at ten 

 o'clock next morning had entirely disappeared." 



Animals are much more frequently struck by lightning 

 than human beings, probably from being more exposed to 

 the storm, and also from taking shelter under trees, which 

 are sometimes struck. Animals are, no doubt, quite as 

 much terrified, if not more so, than human beings during a 

 thundei-storm, and consequently huddle together. The 

 heated moist air rising from then- bodies forms a ready path 

 for the lightning discharge, and consequently we frequently 

 hear of two or more animals being killed by the same flash. 

 The vagaries of lightning are very strange. Sometimes 

 one sheep only in a flock is killed, the othei-s being un- 

 touched, or two horses may be standing side by side, when 

 one is struck and the other uninjured. Colonel ParneU 

 quotes a case in which sixteen natives and five oxen were 

 killed at one discharge on the high road in Natal in 1878. 

 A diver under water in Cole Harboiu-, Halifax, N.S., was 

 rendered insensible, the air-pump having been struck by 

 lightning. Coal mines are not apparently exempt fi-om 

 lightning discharges, as there is evidence to show that 

 on July 12, 1880, lightning actually entered the workings 

 of the Tanfield Moor Colliery. 



When the lightning strikes sand it sometimes fuses it and 

 forms what is called a " fulgurite," which is a kind of 

 vitrified hollow tube. Some of these tubes have been found 

 30 or 40 feet long. Two interesting specimens of fulgurites 

 are to be seen in the British Museum. 



Trees are perhaps the objects most frequently struck by 

 lightning. In some instances the bark only is torn ofi", 

 while in others a large limb or the trunk of the tree itself is 

 completely shattered. The shivering of the trees into small 

 splinters is probably due to the sudden heating of the sap, 



which is driven into steam ; the wood is consequently blown 

 to pieces. Photographs 4 and .5 are reproductions of photo- 

 graphs of some trees which have been struck by lightning. 



ON THE DISRUPTIVE EFFECTS OF 

 LIGHTNING, AND ON DARK FLASHES. 



By a. C. Ranyahd. 



E are indebted to the kindness of Mr. G. J. 

 Symons for the loan of the two photogi-aphs 

 of lightning-struck trees and of the burst 

 boots worn li}' children in Atcham Church 

 when it was struck by lightning ten years 

 ago. Mr. Symons has during the last 

 twenty years made a large collection of 

 photographs of objects shattered and torn by lightning, and 

 we hope that we shall at some future time be permitted to 

 draw still further on his interesting store for the benefit of 

 the readers of Knowledge. 



Frequently only a narrow strip of bark is blown from the 

 side of a Ughtning-blasted tree. The strip of bark often 

 remains attached by its upper end, like the gi-eat splinter 

 in our picture of the poplar in Regent's Park. It must not 

 be assumed too readily from such an appearance that the 

 explosion took place at an appreciably earlier instant at the 

 lower part of the tree than in the part above, indicating, as 

 has often been assumed, that the flash was an upward one. 

 It is possible that the dii-ection of the splinters only indi- 

 cates that the explosive forces acted with greater energy 

 below than above. When we consider the velocity of the 

 current as compared with the time which would be occupied 

 in tearing elastic splinters of wood, this seems to be the 

 more probable explanation. 



When the bark is only blown away, the shining surface 

 of the cambium layer or outer ring of growing cells just 

 below the bark is left exposed ; this is the region where 

 there is most .sap, and it is generally assumed that the explo- 

 sion is caused by the moisture of the growing cells being 

 suddenly converted into steam. But tlie cells of the cam- 

 bium layer do not generally appear to be charred, or as if 

 they had been exposed to such heat as would instantaneously 

 di-ive fluids into vapour. The explosive force also acts occa- 

 sionalh' evidently with great energy in the central parts of 

 the trunk where there are no growing cells. The great oak 

 at East Tisted, shown in the lower picture, is an excellent 

 example of this. The clergyman standing beneath it is the 

 Rev. Wm. Howlett, known to readers of Knowledge by 

 his admirable drawings of sun-spots. He serves us here 

 as a standard of comparison by which the size of the great 

 oak may be more readily realised. 



The vapoiu'-explosion theory will evidently not account for 

 all the disruption which takes place along the line of dis- 

 charge ; frequently lightning shatters stone and sometimes 

 glass, within which there can be no moisture to explode. 

 We know that a sudden local change of temperature 

 will shatter stones sometimes with great violence, producing 

 noises which in the case of meteorites are probably heard 

 over greater areas than any of the artificial explosions pro- 

 duced by modern artillery ; but mere expansion due to the 

 sudden development of heat will not account for the shreds 

 into which the clothes of the Ughtning-struck sawyer 

 referied to by Mr. Man-iott have been torn. The clothes 

 are not charred or singed, except in places, although the 

 bodies of the unfortunate men wei-e badly scorched. In the 

 British Medical Journal for August 4, 1888, one of these 

 sawyers is described as having " bums on the right side 

 from his shoulder to his feet, beaiing the appearance of 



