1871.] 



through Rarefied Media, tyc. 



241 



they remained in spite of all wiping ; he then examined the negative pole, 

 and discovered a minute speck of dirt corresponding to the luminous spots 

 on the positive pole. 



When the filament of wood is removed from the negative pole, there is 

 sometimes a luminosity or glow over a large portion of the surface of the 

 positive ball. If in this state three or four little pieces of wax, or even a 

 drop or two of water, be placed upon the negative pole, corresponding non- 

 luminous spots will be found upon the positive pole, which rotate with the 

 former, but do not with the latter. 



It is therefore evident that there are lines of force existing between the 

 two poles, and by these means one is able to telegraph from the negative 

 to the positive pole to a distance of 8 inches through the air, without any 

 other conductor than that which the electrical machine has constructed for 

 itself across the non-conducting gas. 



The foregoing seems to the author to give a possible explanation of 

 " ball-lightning." If it be possible for there to be a negatively electrified 

 cloud sufficiently charged to produce a flash from the earth to the cloud, a 

 point in the cloud would correspond to the wood projection on the negative 

 conductor : if such a cloud exist, a luminous spot would be seen moving 

 about the surface of the earth, corresponding to the moving point of cloud 

 over it, and thus present phenomena similar to those described by the pri- 

 vileged few who have witnessed this extraordinary natural phenomenon. 



The following experiment shows that, prior to the passage of the electric 

 spark, a channel is prepared for this spark to pass. 



The positive and negative balls of the machine were separated to a 

 distance of 6 or 7 inches, and a common candle-flame was placed midway be- 

 tween them. On rotating the machine, the flame was drawn out on each side 

 just prior to tbe passage of the spark, as shown in the accompanying sketch 

 (PI. III. fig. 3). Sometimes it extended to a width of 5 or 6 inches ; this 

 took place every time the spark passed. It is well known that the dura- 

 tion of this spark is less than the 100 1 Q0Q part of a second ; the flame occu- 

 pied the J or T L part of a second in flying out to make the conducting chan- 

 nel through which the discharge went. 



The author has been informed more than once, by captains of vessels, 

 that when men have been struck by lightning a burn has been left upon the 

 skin of the same shape as the object from which the discharge flew. In 

 one instance he was informed that some brass numbers attached to the 

 rigging, from which the discharge passed to the sailor, were imprinted upon 

 his skin. 



It is now seen that this is perfectly possible if the discharge be a nega- 

 tive one — that is, if the man be + to the brass number. 



VOL. XIX. 



u 



