534 WRITINGS OP JOSEPH HENRY. [1878 



the explosion of a shell under water at the distance of 

 about 300 yards. Within thirty minutes the light-house 

 was struck seventeen times: each stroke was most percepti- 

 bly felt, and could be heard in the keeper's closed dwelling, 

 — resembling in sound the discharge of a shot-gun. Each 

 time the light-house was struck it trembled violently from 

 top to bottom. The whole air seemed pervaded with elec- 

 tricity, and on arising from bed, my bare feet coming in 

 contact with the floor (which was wet from the rain beating 

 in at the window), I received a severe electrical shock which 

 caused my hair to stand straight, and I was compelled to 

 jump into bed and put on shoes before I could venture again 

 onto the floor. One of the men assisting me was so violently 

 affected as to vomit; the other men were similarly affected. 

 The storm continued furiously till midnight, at which time 

 it abated a little until daylight, when the wind hauled to 

 the westward, and at eight o'clock it was blowing furiously 

 again. The storm continued unabated until sunset, when it 

 subsided. On Saturday the weather was fine, and we con- 

 tinued our repairs. The storm was one of the most violent 

 I ever experienced or heard of." 



An additional fact to those given in this letter was obtained 

 through Cap t. Heuer from the same source, viz: each time 

 the light-house was struck, the piles which formed the stable 

 part of the structure seemed to become luminous. This 

 appearance may have been an optical deception, produced 

 by the reflection of the light of the discharge from the various 

 points of the building. This appearance however is not 

 without a parallel in the history of discharges of atmospheric 

 electricity, vertical rods of iron at the moment of a dis- 

 charge having presented a luminous appearance throughout 

 their whole length. 



The physiological effects mentioned were probably due to 

 induction, since during the continuance of the cloud above 

 the light-house, all parts of the building must have been in 

 a highly negative condition, supposing the cloud to be posi- 

 tive. This condition in itself, without variation, would 

 scarcely produce any perceptible effoct on the bodies of the 

 inmates. It would however be in a state of continual varia- 

 tion with the constant changes in the intensity of the action 

 of the cloud above, especially at the moment of the discharge, 



