1841] WRITINGS OF JOSEPH HENRY. 105 



principles. The front of Mrs. Hamilton's house is parallel 

 with the main street, and is nearly in an east and west 

 direction. The building is of brick, with a shingle roof, and 

 is two stories high ; it has on the front, three upper windows, 

 and two windows and a door below; the latter being imme- 

 diately under the western upper window. The chimney is 

 on the eastern end, and the lightning conductor is supported 

 against this. The rod is formed of round iron, three-eighths 

 of an inch thick, and the several parts of it are imperfectly 

 connected by hooks and eyes. It appears to be merely thrust 

 into the ground to the depth of about two feet, and is ter- 

 minated above by three prongs instead of one, the points of 

 which are blunted by long exposure, but do not exhibit any 

 appearance of fusion. The top of the rod is not more than 

 six feet above the ridge of the roof; and since the house is 

 about thirty feet long, the farther end of the ridge is unpro- 

 tected. A point, according to the experiments of Mr. Charles, 

 can only protect a circular space, the radius of which is not 

 greater than twice the height of the point above the plane 

 to be protected. 



The lightning, according to the accounts of several per- 

 sons, came from a cloud situated to the southwest, and the 

 discharge did not strike the most elevated part of the build- 

 ing, but the western end of the horizontal wooden gutter 

 which extends along the front of the house under the eaves. 

 This point is at the greatest possible distance from the ex- 

 tremity of the lightning rod, and perhaps was as near to the 

 cloud as any other part of the building. The discharge im- 

 mediately divided itself into two parts : one of these, and 

 probably the larger, passed along the gutter, which must 

 have been filled with water at the time, to the eastern end 

 of the same, and then down to the earth along an ordinary 

 tinned iron pipe or conductor, which conveys the water from 

 the gutter to the pavement below. Marks of its passage were 

 observed alongthegutter, and particularly near the end next 

 the metallic conductor. The other part of the discharge 

 passed immediately downward through the end of the gutter 

 which first received the shock, to the casing of the window 



