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This seems a proof, that, though the small, sharpened part of the wire must have had a less natural quantity in it before the operation, than the thick, blunt part, yet a greater quantity was driven down from it to the balls. Thence it is again inferred, that the pointed rod is rendered more negative; and, farther, that if a stroke must fall from the cloud over a building, furnished with such a rod, it is more likely to be drawn to that pointed rod than to a blunt one; as being more strongly negative, and of course its attraction stronger. And it seems more eligible, that the lightning should fall on the point of the conductor (provided to convey it into the earth) than on any other part of the building, thence to proceed to such conductor. Which end is also more likely to be obtained by the length and loftiness of the rod; as protecting more extensively the building under it.
It has been objected, that erecting pointed rods upon edifices is to invite and draw the lightning into than; and therefore dangerous. Were such rods to be erected on buildings, without continuing the communication quite down into the moist earth, this objection might then have weight; but, when such complete conductors are made, the lightning is invited, not into the building, but into the earth, the situation it aims at, and which it always seizes every help to obtain, even from broken, partial metalline conductors.
It has also been suggested, that, from such electric experiments, nothing certain can be concluded as to the great operations of nature; since it is often seen, that experiments, which have succeeded in small, in large have failed. It is true, that in mechanics this has sometimes happened. But, when it is considered, that we
owe our first knowledge of the nature and operations of lightning to observations on such small experiments; and that, on carefully comparing the most accurate accounts of former facts, and the exactest relations of those that have occurred since, the effects have surprisingly agreed with the theory; it is humbly conceived, that in natural philosophy, in this branch of it at least, the suggestion has not so much weight; and that the farther new experiments, now adduced in recommendation of long, sharp-pointed rods, may have some claim to credit and consideration.
It has been urged, too, that, though points may have considerable effects on a small prime conductor at small distances; yet, on great clouds and at great distances, nothing is to be expected from them. To this it is answered, that in those small experiments it is evident the points act at a greater than the striking distance; and, in the large way, their service is only expected where there is such nearness of the cloud as to endanger a stroke; and there, it cannot be doubted, the points must have some effect. And, if the quantity discharged by a single pointed rod may be so considerable as I have shown it, the quantity discharged by a number will be proportionably greater.
But this part of the theory does not depend alone on small experiments. Since the practice of erecting pointed rods in America (now near twenty years), five of them have been struck by lightning, namely, Mr. Raven's and Mr. Maine's in South Carolina, Mr. Tucker's in Virginia, Mr. West's and Mr. Moulder's in Philadelphia. Possibly there may have been more, that have not come to my knowledge. But, in every one of these, the lightning did not fall upon the body of the house, but precisely on the several points of the rods; and, though the conductors were sometimes not sufficiently