;66 



NA TURE 



\August 15, 1889 



"'The city of Samaskuta, which was situate in the interior 

 of Siinnatia, became sea, the water of which was very clear, and 

 which was afterwards called the lake Sinkara.^ This is the 

 origin of the feparation of Sumatra and Java.' " - 



Whether we are justified in accepting this date (a. d. 416) as 

 that at which the very grand eruption of Krakatab, and the 

 accompanying subsidence which led to the separation of Java 

 and Sumatra, actually took place, I am not prepared to say. It 

 may be that, as in many similar cases, the floating traditions of 

 a grand catastrophe attached themselves to a subsequent event 

 of a similar character. It is certainly very interesting to learn, 

 liowever, that in the fifth century very grand volcanic outbursts 

 Were taking place in the district in question ; and that a belief 

 existed in the former connection of the islands of Java and 

 Sumatra. Nor is it unimportant to discover that tradition is in 

 complete harmony with scientific reasoning in assigning the 

 separation of the two islands to actions occurring concurrently 

 with great volcanic outbursts. 



In concluding this note, I must express my great obligations 

 to Mr. Baumgarten and Dr. Rost for bringing these important 

 records under my notice. John W. Judd, 



On some Effects of Lightning. 



Pkof. McMillan's interesting letter in Nature of July 25 

 (p. 295) contains some minute details of the eflfects of a light- 

 ning-stroke on a house near Calcutta, on June 8 last. I agree 

 with the writer that such cases are of value to electrical science, 

 especially when reported by a competent observer. In Prof. 

 McMillan's excellent letter there is one word to which I object, 

 and that is " vagaries," as applied to electricity at high poten- 

 tial. When lightning enters a house, it is as much subject to 

 law as when it flashes from the cloud to the earth, and does not 

 behave with the whim, caprice, or freak implied by the word 

 "vagary." In the absence of continuous conductors, the elec- 

 trical discharge drags into its path light, conducting substances, 

 which assist iis progress, and by means of which it can strike 

 through considerable distances and in various directions, as in 

 the case before us. As to the effect of the discharge on the air 

 of the house, Mr. McMillan appears to have made a real ad- 

 vance towards the solution of a difficult problem — namely, What 

 is the origin of the powerful odour produced by a lightning- 

 discharge within an inclosed space, such as a room or a ship ? 

 In most cases, the odour is compared to that of burning sulphur 

 — "the ship seened to be nothing but sulphur," was entered in 

 the log of the Montagtie, after having been struck by lightning. 

 Now as far back as 1785, Cavendish's famous experiment 

 proved that electrical discharges in a confined mass of air 

 lead to the formation of nitric acid, and Liebig found that 

 acid in seventeen samples of rain-water collected during 

 thunder-storms. Nevertheless, with these facts before him. 

 Snow Harris wrote : " From whence this odour arises is still 

 an interesting problem in physics," and he declines to discuss 

 " those chemical views v hich some able philosophers have enter- 

 tained of the nature of the odour emitted." Arago also states 

 that the odour is generally compared to that of burning sulphur ; 

 but he adds: "others compare it to phosphorus, others to 

 nitrous gas " ; and significantly remarks : ' ' L'odeur de gaz nitreux 

 serait le plus iacile a expliquer." Now, Prof. McMillan has 

 shown that nitrogen teioxide, more or less diluted with air, was 

 sufficient in the case so ably reported by him, to account for the 

 colour and odour of the atmosphere produced within the house 

 by the electric discharge. "The whole house seemed to be 

 filled with an orange-coloured gas, mixed with clouds of dust 

 affecting the breathing like fumes of burning sulphur," is the 

 description given by the occupier of the house. 



Another point of interest in this valuable communication is 

 the introduction of ball-lightning. Arago is sceptical as to the 

 existence of ball-lightning {eclairs en honk), or that which moves 

 through the air at a comparatively slow rate, appearing like a 

 luminous ball or globe of fire. Faraday is also equally sceptical. 

 But the well-attested cases of what we name ball-lightning, and 

 the Germans Kit'^clblitz, are so numerous that they can no longer 

 be termed, in Arago's language, " a stumbling-block {fierre 

 d'achoffcnicnt) for meteorologists." Snow Harris properly 

 describes these luminous balls as a kind of brush or glow 

 discharge. In the well-known case of the Montague^ the 



^ " The well-known^Lake of the ' Menang-Kebo' countn-." 

 - Seethe '■ Kraltatao Eruption and thejavane.se Chronicles "in Tit'i'ners 

 Kcc ■rd f^r August 1889 (third series, v„l. i. pt. 3). 



luminous ball was seen rolling on the surface of the 

 water towards the ship from to windward ; evidently a brush 

 discharge, or St. Elmo's fire, produced by some of the polarized 

 atmospheric particles, yielding up their electricity to the 

 surface of the water. On nearing the ship, the point of discharge 

 became transferred to the head of the mast, and, the striking 

 distance being thus diminished, the whole system returned to its 

 normal state^that is to say, a disruptive discharge ensued 

 between the sea and the clouds, producing the usual phenomena 

 of thunder and lightning, described by the observers as "the 

 rising of the ball through the mast of the ship." In Prof. 

 McMillan's case I do not understand his remark that " no second 

 ball was seen to enter from the opposite side to meet the first, 

 and so produce the apparent explosion." Surely a second ball 

 was not necessary to produce the effect described — namely, " an 

 intensely brilliant ball of yellow fire, about 6 or 7 inches in 

 diameter, which passed from one end of the room to the other at 

 a pace just sufficiently s'ow to allow it to be readily followed by 

 the eye : it appeared to be momentarily checked, then burst 

 with a deafening report, which shook the whole house." In 

 other words, it passed from a brush into a disruptive discharge. 



Lastly, we have anoiher remarkable confirmation of the fact 

 that a lightning-conductor does not afford protection to surround- 

 ing objects. According to the French theory, a lightning-rod 

 affords protection over a circle equal to twice its radius. But 

 there are numerous cases to prove that no such radius of pro- 

 tection exists. The Endyniion frigate, at Calcutta, in March 

 1842, was furnished with a chain conductor on the mainmast, 

 but the lightning striick the foremast, shivered the topgallant 

 and topmast, and damaged the lower mast. The mast struck 

 was not above 50 feet from the mainmast. A somev/hat similar 

 accident happened to the Etna in Corfu, in January 1830. So also 

 in the case that excited so much discussion at the time, the 

 Board-house at Purfleet was struck on May 12, 1777, at a point 

 about 40 feet from the conductor. A similar case occurred at 

 the Poor-house at Heckingham in June 1781. So also in the 

 recent Calcutta case, there was a conductor at one end of the 

 building, projecting 8 or 9 feet above the roif-level. But the 

 lightning entered the house by an iron-covered hatchway, 70 feet 

 from the conductor, and near to a shell factory, which bristled 

 with conductors. 



Prof. McMillan properly attaches great value to such cases as 

 the one he r'eports, leading as they do to the conditions which 

 should govern the protection of buildings. In the course of a 

 long experience, I have noticed that the profession which should 

 be the best instructed on the subject, is — I hope I may say was — 

 the worst. When the new buildings for the Cholmeley School 

 at Highgate were being erected, the head master consulted me 

 as to the erection of a lightning conductor, and asked me to see 

 the architect. That gentleman called on me and said, " We 

 never put up these things ; we don't approve of them. I never 

 erected one in my life, and don't know how." I once visited a 

 church in Rutlandshire, that had been restored by Sir Gilbert 

 Scott. The r^ector took me to one of the gable ends, and said, 

 " You see, we have a lightning conductor, properly insulated by 

 means of glass rings." I replied that on visiting the granite 

 lighthouse at the end of the Plymouth breakwater, I noticed 

 that Faraday, in fixing a lightning conductor, had caused a spiral 

 groove to be cut inside the shaft from top to bottom, for the 

 insertion of a massive copper band, so as to make the conductor 

 an integral part of the building. Snow Harris's method of pro- 

 tecting a ship applies also to a building. At whatever part of 

 the ship or building the lishtning may strike, it ought to find an 

 easy metallic path to the sea, or to the earth. The late Prof. 

 Clerk Maxwell, writing to me as to the best method of securmg 

 a building, pi-oposed to inclose it with a network of good con- 

 ducting material, such as a copper wire, No. 4 British wire 

 gauge, to be carried round the foundation of the house, up each 

 of the corners and gables, and along the ridges. Further details 

 would occupy too much space on the present occasion. 



Highgate, N., August I. C. Tomlinson. 



Some weeks ago, two trees were struck by lightning near St. 

 Albans, in Hertfordshire, the effects of which are most unusual. 

 The two trees stood near each other in a wood called Symonds 

 H}de ^^'ood. Assuming that the lightning struck downwards, 

 it is easy to see in one case where the damage began — namely, 

 at a place where a branch had by some means been broken off" 

 formerly, leaving a ragged break, into which no doubt water 

 had soaked. Thence for some feet downward the effect was 



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