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M. Calandrini says further, that he himself has been eye-witness of the effects of lightning coming into a room, which had received much damage from it. That he looked for the place it went out at, and after long search perceived that it had followed the wire of the bell, which had conducted it through a very inconsiderable hole into the next room; from whence it had opened itself a passage into a back yard. This accident was at that time thought very extraordinary, being anterior to Dr. Franklin's experiment.
To M. Calandrini's questions I have sent the following answers.
I. The apparatus, used at Philadelphia, consists either of a long iron rod, placed upon the highest part of an house, or other building; or, of a shorter rod, inserted into a long wooden pole, placed in the same manner. The iron rod, mentioned by Mr. Kinnersley in the Philosophical [1] Transactions, and which probably preserved the house in Philadelphia upon which it was placed, extended in height about nine feet and a half above a stack of chimnies, to which it was fixed; but he supposes that three or four would have been sufficient. These rods are pointed at their upper extremity. It is indifferent, which of these two are used, provided that they are of height enough to reach above the chimnies, or any other part of the edifice. Connected to, or suspended from, the metal of these, a metallic wire, generally of iron, is conducted, in the easiest and most convenient manner, to the nearest water, viz. to the well of the house, or any other water in the neighbourhood.
- ↑ Vol. LIII. page 95.
