306 On Lightning Conductors to Powder Magazines. [No. 99. 



trician, has recently published some views regarding this spark, 

 which require a cursory notice. Mr. Harris, when ten years ago 

 he proposed his system of ship conductors, was either unaware 

 of the occurrence of this spark, or held it in such little respect 

 that he actually led one of his conductors through the after 

 powder magazine, and he has recently induced the Lords of the 

 Admiralty to order this system to be adopted through the 

 navy. 



34. Mr. Harris admits the existence of the lateral spark, but 

 attributes it to what is commonly called the " residual charge." 

 Thus after discharging a battery, it is well known that a small 

 secondary charge collects* and will give a spark or shock to any 

 conductor touching both the coatings. 



35. I repeat, that it is but little consequence what the cause 

 or nature of the spark in question be. It is its existence only 

 that should influence this question. But if Mr. Harris will 

 repeat the experiment described at para. 30, he will find the 

 explosion of the cannon to occur at the very same instant of 

 time as the discharge of the jar, and that after this, he will still 

 succeed in obtaining the residual discharge on contact of the 

 inner and outer coatings. 



36. The accident which befel Her Majesty's ship Rodney last 

 year in the Mediterranean, shows the occurrence of the lateral, 

 or extra discharge in a form which scarcely admits of mistake ; 

 the flash struck the main-top-gallant mast, and escaped from 

 the mast seven feet above the deck, and was seen by all on 

 deck to go over the lee-nettings, and strike the sea a short dis- 

 tance from the ship. 



Sparks were seen by many of the officers between decks, and 

 many of the men declared they saw balls of fire on the lower 

 deck, and ran after them to throw them out, 



Here is another instance of lateral or indirect effect. At the 

 moment Dr. Goodeve's house was struck, Mr. Hutchins sitting 

 in a room on the ground floor, several feet from the course 

 of the lightning, received a severe shock. Whatever produces 





