las PHILOSOPHICAL TRANSACTI0W3. [aNNO I764, 



by Mr. Kinnersley in the Phil. Trans. Abridged, vol. xi. p. 702, and which 

 probably preserved the house in Philadelphia on which it was placed, extended in 

 height about Q-J- feet above a stack of chimneys, to which it was fixed ; but he 

 supposes that 3 or 4 would have been sufficient. These rods are pointed at their 

 upper extremity. It is indifferent which of these two is used, provided they are 

 high enough to reach above the chimnies, or any other part of the edifice. Con- 

 nected to, or suspended from, the metal of these, a nietallic wire, generally of 

 iron, is conducted in the most convenient manner to the nearest water, viz. to 

 the well of the house, or any other water in the neighbourhood. 



2. This method, wherever it has been employed, has hitherto perfectly ans- 

 wered the intention ; no house in Philadelphia, or in any other place I have 

 heard of, having suffered from the effects of lightning, where this apparatus has 

 been erected. The improvements I should recommend would be, first, that as 

 iron wire soon becomes rusty, and when rusty to the centre is unfit for the pre- 

 sent purpose; and as brass wire is, when long exposed to the weather, exceed- 

 ingly brittle and liable to snap asunder, the wire should be of copper; and of a 

 size not less than that of a large goose- quill. Secondly, I prefer its being con- 

 ducted, from the rod at the top to the water below, on the outside of the build- 

 ing, and thus prevent the lightning from coming within the building. On 

 houses where there are gutters and spouts of lead to carry off the rain, the wire 

 need only be conducted to the lead of the gutters; and attention be had that the 

 gutters and the spouts coming from them are in their whole length in contact, 

 or very nearly so, one with the other. If the leaden spouts do not reach to the 

 bottom of the building, a slip of lead, such as is employed for the gutters, and 

 about an inch wide, should be fastened to the bottom of one or two of the 

 spouts, and conducted to the water. If such a slip of lead was to be conducted 

 firom the rod at top to the gutters, it might with equal advantage be substituted 

 for the copper wire: or further, a slip of lead of this kind may be connected with 

 the rod at the top of the house; and where there are no leaden gutters or spouts, 

 may be conducted on the outside of the house down to the water, as before 

 mentioned. I would recommend likewise an increase of their number; as the 

 effects of one apparatus of this kind can extend only to a certain distance, and 

 that to no great one; and the security, where mischiefs from lightning are fi-e- 

 quent, must arise from their number. In countries and places so circumstiuiccd 

 no house or other building should be without ohe at least ; large edifices ought 

 to have several. The number should be in proportion to the size of the building. 



3. In powder magazines I should recommend the apparatus to be detached 

 from the building itself; and to be only placed as near it as might be. Powder 

 magazines should never be constructed so as to cover a large quantity of ground. 

 If security from lightning was considered in their construction as a considerable 



