Of Running during a Thunder-Storm. 139 



I is low. Thus, whatever diminishes the density of the air to a 

 certain point, tends, more or less, to attract lightning. Now, a 

 man who runs in a calm, leaves a space behind him in which the 

 strokes of lightning will find readier transmission. I here add a 

 fact, the circumstances of which have been communicated to me 

 by my illustrious fellow member, Admiral Roussin, and which, 

 perhaps, will be considered as somewhat favourable to the con- 

 jectures we have been making. The frigate La Junoriy on her 

 way to India, was assailed on the 18th of April 1830, near the 

 Canaries, by a violent thunder-storm, during which, in spite of 

 her conducting-rod, she was struck with lightning. The fact of 

 her being so struck appears no ways doubtful. In fact, im- 

 mediately after the flash, there was a strong smell of sulphur all 

 over the vessel. Besides, those who were on the quarter-deck 

 saw a stream of light fly off^ from the conductor. This stream or 

 flash was seen at a point situated half-way between the {grand* 

 hune and the hartingage) top-gallant-mast and the halyards, and 

 fell into the sea to the larboard, whilst the extremity of the 

 conductor-chain led the sea on the other side, or to starboard. 

 I may here add, that at the moment of the flash, one of the 

 sailors was completely asphyxiated, and for a time was supposed 

 to be dead. After the accident, it was found upon examination 

 that the chain, composed of copper-wire, twisted like common 

 cordage, and forming a cylinder of about f ths of an inch iu dia- 

 meter, had not been fractured in any part. The point only of 

 the metallic vein, screwed to the top of the mast, and with which 

 the conducting chain was in communication, was somewhat burnt. 

 The fact of the lateral discharge of the lightning, darting from 

 the conductor, is completely established by all these details; but 

 we have still to discover the explanation. The first method of 

 accounting for it which occurs to the mind, is, that the metallic 

 chain was of much too small diameter. It adds force to this ob- 

 jection, if we moreover suppose, that at the moment of the flash 

 the lower extremity of the chain was not really under water. 

 This extremity was attached to a sheet of copper, usually fixed 

 about a couple of feet below the ship'*s water-mark. On the oc- 

 casion of this thunder-storm the copper sheet was starboard ; so 

 was the wind ; and it is stated to have been very strong. All these 

 circumstances lead to the supposition that the vessel must have 



