100 ATMOSPHERIC ELECTRICITY. 



are brought to an end either along- their whole front, or only part of 

 it, when they reach the banks of a large river. 1 



Some curious problems are presented by the detailed structure of 

 lightning flashes. Although these lie outside the range of the present 

 lecture, reference must be made to the very beautiful photographs of 

 lightning flashes taken both in this country and abroad. The ordinary 

 forms which lightning takes are familiar to all, but a good deal of 

 mystery still surrounds the so-called globular lightning. The manner 

 in which this form appears is best described in the words of eye- 

 witnesses. 



Dr. A. Wartmann gives to the Physical Society of Geneva the fol- 

 lowing account of what he saw: 2 



"At half-past 6 o'clock in the evening I drove from Versoix to Gen- 

 thoud. On the Malagny road I heard the coachman say he did not 

 know where he was. His eyes were so much fatigued by the frequent 

 and intense lightning discharges that he was blinded and could not, 

 even in the intervals, see the road, in spite of the good lanterns along- 

 side. I stepped on to the box and took the reins. We had barely 

 passed the principal gate of the grounds of Dr. Marcet when I became 

 conscious of a bright and lasting luminosity behind me. Thinking it 

 was a fire, I turned round, and saw, at a distance of, roughly, 300 meters, 

 a ball of fire of about 40cm. diameter. It traveled in our direction with 

 a velocity about equal to that of a bird of prey, and left no luminous 

 trail behind. Just as the ball had overtaken us, about 24 meters to our 

 right, it burst with a terrific noise, and it seemed to me as if lines of 

 fire started from it. We felt a violent shaking, and remained blinded 

 a few seconds. As soon as I regained power of distinguishing objects 

 I saw that the horses had turned at a right angle to the carriage, with 

 their chests in the hedge, with drooping ears and all signs of great ter- 

 ror. I returned on the following day to the place where I had seen the 

 ball explode, but could find no sign of any damage. At a distance of 

 100 meters I found that a group of three trees, bordering a wood, had 

 their upper branches singed, but it is not possible to say whether this 

 was due to the discharge which I had seen." 



The following is a translation of an account given by Mr. H. W. Roth 

 (Meteorologische Zeitschrift, 1889, p. 231) : 



"During the thunderstorm of May 19, 1888, at about 6 p. m., a flash 

 of lightning took effect which seems to me remarkable from a physio- 

 logical point of view. The dealer Werner, from Ellerbruch, and his son 

 (16 years old), with a one-horse conveyance containing rags, were on 

 the road which leads from here to the village of Ottensen, about 3 miles 

 away in a southwesterly direction. The father had been left a little 

 behind, and the son was occupied in giving bread to the horses, when 

 he found himself suddenly surrounded by light, and noticed a fiery ball, 

 about the size of his fist, moving toward him along the back of the 

 horse. Then he lost consciousness. He felt no concussion. The father, 

 on approaching, saw the horse's limbs still contracting, and at first he 

 thought his son was dead, but succeeded, after considerable efforts, in 

 bringing him back to life in about three-quarters of an hour. The horse 

 was dead." 



1 Bebber, "Meteorologie," p. 255; Bornstcin, Archiv der Seewarte, VHl, 1885. 

 - Arch, des Sci. Phys. et Nat. (3) Vol. XXI, 1889. The above account is translated 

 from the Meteorologische Zeitschrift, 1889. 



