Prof. W. M. Thornton on Thunderbolts, G31 



horizontally some feet above the earth's surface. It is seen 

 more often at sea than on land, and both vertical and horizontal 

 movements are recorded in each case. One of the most 

 interesting records of its appearance is given in an account 

 of a storm at sea in Hakluyt's Voyages by Pedro Fernandez 

 de Quiros, three falling in one day. Ball lightning appears 

 to move under gravitative action on a mass somewhat denser 

 than air, or horizontally in a feeble air-current or electric 

 field offeree. It has been observed to follow the course of a 

 conductor such as a water-main, and in most cases to burst 

 on reaching water. It has also been seen to burst in mid-air. 

 That it has some elastic cohesion is shown by its spherical 

 shape and by its rebounding from the earth — in one case at 

 least — after falling vertically. The features of its end are 

 significant ; the ball simply ceases to be and an explosion 

 wave travels outwards from the spot. In all cases its dis- 

 appearance is followed by a strong smell of ozone. 



There are records of its curious selective behaviour in the 

 neighbourhood of conductors. Tims a fireball came down a 

 chimney, approached a person in the room (who slowly 

 avoided it), retired up an old flue papered over, breaking 

 through the paper, and finally burst with great violence on 

 reaching the chimney-top, doing considerable damage. It 

 may be inferred from this that its undoubted immense 

 energy is not in the form of any surface charge which 

 would have had many opportunities of dissipation in such a 

 journey. 



From the circumstances of its origin, it is clear that there 

 can be nothing present in it but the gases of the atmosphere. 

 That their molecular condition is abnormal is shown by the 

 light which permeates the whole, and the only possible infer- 

 ence from this is that there is atomic rearrangement proceeding 

 actively within the mass. This blue colour is characteristic 

 of a state of air in which there is proceeding intense electric 

 dissociation, as for example in the immediate neighbourhood 

 of a highly charged needle-point. The chief product of 

 molecular change under electric stress in air is ozone. This 

 is shown by the fact that at a charged point ozone is given off, 

 freely at the negative, and to a much less extent at the positive 

 pole. Nitric oxide is not produced in this case, and it appears 

 to be necessary to have streams of sparks to give rise to the 

 formation of nitrogen compounds in air. The absence of 

 nitrogen compounds is shown by the action of the electric 

 wind from charged points on paper dipped in a solution in 

 alcohol of tetramethyl p. p. diamido-diphenyl-methane, which 

 in the presence of ozone turns violet-blue and with nitrogen 



