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. For though I have reason to believe, that the wire communicating with the ground would prevent the mischiefs of a thunder cloud, which came near an apparatus of this sort; yet as water is a more ready conductor than the ground, it should, if possible, be insisted upon in this particular case, and employed. Mr. West's apparatus, described by the before-mentioned Mr. Kinnersley, terminated in an iron stake, driven four or five feet into the ground; nevertheless the earth did not conduct the lightning so fast but that, in a thunder storm, the lightning was seen to be diffused near the stake two or three yards over the pavement, though at that time very wet with rain. It is presumed, that had this iron stake been placed in water instead of earth, the lightning had not been visible, on account of the water's receiving the electric matter more readily than earth. Where this apparatus therefore is applied to powder magazines, it should certainly terminate in water. At Mr. Hamilton's at Cobham, about twenty miles from hence, where an apparatus of this sort was erected upon an high and greatly-exposed building, as there was no water but at a great distance, the bottom of the wire was placed deep in an hill of moist sand. If, instead of one wire, two, three, or more, were adapted to the brass rod in this manner, and conducted to the water, or if the brass rod itself was continued to the water, I should consider it, in extraordinary cases, as an additional security. This will explain my sentiments upon the third, fourth, and sixth questions.

V. As the expectation of the utility of this apparatus is presumed to be the preventing of the accumulation of electricity in its neighbourhood, by