I electrified a silver fruit-can on an electric stand, and then lowered into it a cork ball of about an inch in diameter, hanging by a silk string, till the cork touched the bottom of the can. The cork was not attracted to the inside of the can, as it would have been to the outside, and though it touched the bottom, yet, when drawn out, it was not found to be electrified by that touch, as it would have been by touching the outside. The fact is singular. You require the reason? I do not know it. Perhaps you may discover it, and then you will be so good as to communicate it to me. I find a frank acknowledgment of one's ignorance is not only the easiest way to get rid of a difficulty, but the likeliest way to obtain information, and therefore I practise it. I think it is an honest policy. A note appended to this letter runs as follows:-- Mr. F. has since thought that, possibly, the mutual repulsion of the inner opposite sides of the electrized can may prevent the accumulating an electric atmosphere upon them, and occasion it to stand chiefly on the outside. But recommends it to the further examination of the curious. The explanation in this note is the correct one, and from the fact that in the case of a completely closed hollow conductor the charge is not only _chiefly_ but _wholly_ on the outside, the law of inverse squares above referred to follows as a mathematical consequence. On writing to M. Dalibard, of Paris, on June 29, 1755, Franklin complained that, though he always (except once) assigned to lightning-rods the alternative duty of either _preventing_ a stroke or of _conducting_ the lightning with safety to the ground, yet in Europe attention was paid only to the _prevention_ of the stroke, which was only a _part_ of the duty assigned to the conductors. This is followed by the description of the effect of a stroke upon a church-steeple at Newbury, in New England. The spire was split all to pieces, so that nothing remained above the bell. The lightning then passed down a wire to the clock, then down the pendulum, without injury to the building. "From the end of the pendulum, down quite to the ground, the building was exceedingly rent and damaged, and some stones in the foundation-wall torn out and thrown to the distance of twenty or thirty feet." The pendulum-rod was uninjured, but the fine wire leading from the bell to the clock was vaporized except for about two inches at each end.