May 1, 1898.] 



KNOWLEDGE. 



97 



pbosphuretted hydrogen in small quantities, which, stream- 

 ing up into the atmosphere, may present that faint 

 appearance linown as a corjisf-ciitulle. In Wales an 

 appearance of this kind was said to denote a coming 

 funeral, and few of the people of Carmarthen formerly 

 died without having seen their dcallt-lli/lit, just as in other 

 parts, Northumberland for example, some people saw their 

 u'dff or u-hiji' as a death token, which is similar to the 

 Scotch wriiith, or the appearance of a living person to 

 himself or others. Many years ago the Austrian chemist 

 ^'on Eeichenbach examined a numberof patients in various 

 parts of Germany and Austria who were very sensitive to 

 the action of light. On taking one of these by night into 

 a churchyard, he declared that every grave was luminous. 

 A very sensitive eye is required to see these corpse-candles, 

 and we need not be surprised that a good deal of superstition 

 is connected with them. But phosphorescent meteors, as 

 well as light carburetted hydrogen meteors, are now rarely 

 seen. The latter have been extinguished by drainage and 

 agriculture, and if the former occasionally appear, they do 

 not attract much attention now that their nature is under- 

 stood and their advent accounted for. 



III. — Electrical Meteors. 

 But if the two former kinds of meteors are now but rarely 

 seen, those of the third kind frequently appear, and are 

 likely to continue to do so, since they belong to one of the 

 great forces of Nature which is always active and every- 

 where present, while the other two are natural indeed, but 

 local and accidental in their action. 



In 1752 Franklin, by his famous kite experiment, proved 

 the identity of lightning with common electricity. The 

 action of a thunder-cloud is to throw by induction a portion 

 of the earth's surface lying beneath it into an opposite 

 electrical state. If the cloud be positive or + , the earth 

 will be negative or — . This change is brought about by 

 the polarization of the intervening air ; that is, the upper 

 half becomes - , the lower half -t- , and so throughout, until 

 the -i- half of the lowest particle throws the earth into an 

 opposite or - state. Supposing this action to go on among 

 the innumerable particles of the dielectric or non-conduct- 

 ing air that separate the cloud from the earth, the -f half 

 of each particle becomes more + , and the — half more — , 

 until the strain or tension is such that the system breaks 

 down, and a disruptive discharge of electricity takes place 

 between the cloud and the earth. 



Soon after Franklin's experiment it was discovered that 

 the electrical condition of the air did not depend on 

 the action of a thunder-cloud, but that in different states 

 of the weather, under a cloudy or a clear sky, the air is 

 sensibly electric. In fine weather the air is + and the 

 ground - , and in the course of the twenty-four hours certain 

 variations take place, consisting of two maxima and two 

 minima. The former are probably due to the conducting 

 property of moisture, which brings down electricity from 

 the upper regions, while the dispersion of that moisture by 

 the heat of the sun seems to give occasion to the minima. 

 The electricity of rain, snow, hail and fog is sometimes + 

 and sometimes - . 



But there are occasions when atmospheric electricity 

 assumes a high potential, and gives rise to many curious 

 and interesting effects, so varied that I cannot do much 

 more than glance at them. One tj'pical case, however, may 

 admit of some little detail ; it is related in the " Memoirs of 

 General Marbot," published a year or two ago. The general 

 accompanied Napoleon the First in his invasion of Kussia, 

 and during the retreat of his cavalry regiment he saw 

 before him one night a number of lights, which he mistook 

 for the bivouac fires of the enemy. He sent out scouts to 

 ascertain what force lay before him, and it was reported at 



50,000, while he had less than 700 men. While debating 

 what course to pursue, the lights began to appear on his own 

 men. He at once recognized them as ffiu- folhtx, a term 

 applied by the French to low-lying meteors before theit 

 origin was understood. The general's explanation of the 

 phenomenon cannot be accepted. He had already remarked 

 that a marsh over which he had passed was dry, and yet 

 he accounts for the meteor by supposing it to have been 

 produced by the emanations of the marsh condensed by a 

 slight frost after a hot autumn day. " En peu de temps 

 le regiment fut couvert de ces feux gros comma des ceufs, 

 ce qui amusa beaucoup les soldats." 



The general's account was written from recollection 

 long after the event described, and may thus have been 

 unintentionally embroidered. The imagination of the 

 scouts who mistook the lights for the bivouac tires of a 

 large army, and the dazed sight of the general, who saw 

 dt'n miliiiTx de fcu.r suddenly cover the ground he had lately 

 quitted, were natural exaggerations. The ground just quitted 

 he described as sitne dans iin has fond, sur un trk x-aste marais 

 desseche. Hence the marsh, being dry, could not furnish 

 an inflammable gas, and even had it done so and the gas 

 been set on fire, the flames would not have appeared first 

 on the hills, and afterwards in the plain, nor could they 

 have been seen playing upon the soldiers. The phenomena 

 are, however, quite consistent with what is known of 

 electrical action, a similar example of which is related by 

 Arago as having occurred to some French engineer officers 

 in Algiers on the evening of the 8th May, 1831. They were 

 walking with uncovered heads on a terrace, when the hair 

 of each stood on end, and little jets of electric Hght issued 

 from them. When the officers raised their hands, similar 

 jets played upon their fingers. 



Such phenomena as these formerly struck terror into 

 men's minds, and we ought to be grateful to science for 

 reducing them under natural laws. Shakspeare, in his 

 tragedy of Julius Casur, describes with his usual graphic 

 power the phenomena, and the feeling excited by them. 

 Casca exclaims : — 



" Either there is ii civil strife iu heaven. 

 Or else the world, too saucy with the goiU, 

 Incenses them to send destruction. 



* * * * A common slave 



Held up his left hand, which did Hanie and huru 

 Like twenty torches joiu'd, and yet lii ■ hand, 

 Not sensihle of fire, remained unscoreh'd. 



* # . * # And there were drawn 

 Upon a heap a hundred gha^tl\■ women. 

 Transformed with their fear, Tiho swore thev saw 

 Men all in fire w.ilk up and down tlie streets." 



What Casca thus graphically described, and accompanied 

 with so much horror, now belongs to the order of natural 

 phenomena. In .June, 1880, at Clarens, near the Lake of 

 Geneva, the air in the afternoon of the 17th was in a very 

 excited state, and a cherry tree, measuring about a yard in 

 circumference, was struck by hghtning, and shivered into 

 matches. A little girl who had been gathering cherries, 

 and was now about thirty paces from the tree, appeared to 

 be literally wrapped in a sheet of fire. Some men who 

 were working in a vineyard close by saw the electricity 

 play about her, but they fled in terror from the spot. In 

 a cemetery close by, six persons, separated into three 

 groups, none of them within 250 paces of the cherry tree, 

 were enveloped in a luminous cloud. They said they felt 

 as if they were being struck in the face with hailstones or 

 fine gravel, and when they touched each other sparks 

 passed from their fingers' ends. At the same time a 

 luminous column was seen to descend, and the electricity 

 was distinctly heard as it ran from point to point of an 

 iron railing in the cemetery. None of the persons referred 

 to were hurt ; they only complained of an unpleasant 



