EXPERIMENT III.

Instead of pinching the point between the thumb and finger, as in the last experiment, keep the thumb and finger each at near an inch distance from it, but at the same height, the point between them. In this situation, though the point is fairly exposed to the prime conductor, it has little or no effect; the electrometer rises to the height of a full charge. But the moment the fingers are taken away, the ball falls quick to the stem.

OBSERVATION.

To explain this, it is supposed, that one reason of the sudden effect produced by a long naked pointed wire is, that (by the repulsive power of the positive charge in the prime conductor) the natural quantity of electricity contained in the pointed wire is driven down into the earth, and the point of the wire made strongly negative; whence it attracts the electricity of the prime conductor more strongly than bodies in their natural state would do; the small quantity of common matter in the point, not being able by its attractive force to retain its natural quantity of the electric fluid, against the force of that repulsion.-But the finger and thumb being substantial and blunt bodies, though as near the prime conductor, hold up better their own natural quantity against the force of that repulsion; and so, continuing nearly in their natural state, they jointly operate on the electric fluid in the point, opposing its descent and aiding the point to retain it; contrary to the repelling power of the prime conductor, which would drive it down.-And this may also serve to explain the different powers of the point in the preceding experiment, on the slipping down the finger and thumb to different dis

tances.

its atmosphere was drawn from the end where the electrometer is placed to the part immediately over the large body, and there accumulated ready to strike into it with its whole undiminished force, as soon as within the striking distance; and, were the prime conductor moveable like a cloud, it would approach the body by attraction till within that distance. The swift motion of clouds, as driven by the winds, probably prevents this happening so often as otherwise it might do: for, though parts of the cloud may stoop towards a building as they pass, in consequence of such attraction, yet they are carried forward beyond the striking distance, before they could by their descending come within it.

EXPERIMENT V.

Attach a small light lock of cotton to the underside of the prime conductor, so that it may hang down towards the pointed wire mentioned in the first experiment. Cover the point with your finger, and the globe being turned, the cotton will extend itself, stretching down towards the finger, as at a; but on uncovering the point, it instantly flies up to the prime conductor, as at b, and continues there as long as the point is uncovered. The moment you cover it again, the cotton flies down again, extending itself towards the finger; and the same happens in degree, if (instead of the finger) you use, uncovered, the blunt end of the wire uppermost.

OBSERVATION.

To explain this, it is supposed that the cotton, by its connexion with the prime conductor, receives from it a quantity of its electricity; which occasions its being attracted by the finger that remains still in nearly its natural state. But when a point is opposed to the cotton, its electricity is thereby taken from it, faster than it can at a distance be supplied with a fresh quantity from the conductor. Therefore being reduced nearer to the natural state, it is attracted up to the electrified prime conductor; rather than down, as before, to the finger.

Supposing farther that the prime conductor represents a cloud charged with the electric fluid; the cotton, a ragged fragment of cloud (of which the underside of great thunderchimney or highest part of a building.-We clouds are seen to have many) the finger, a then may conceive that when such a cloud passes over a building, some one of its ragged by the chimney or other high part of the ediunder-hanging fragments may be drawn down fice; creating thereby a more easy communication between it and the great cloud.-But a long pointed rod being presented to this fragment, may occasion its receding, like the cotton, up to the great cloud; and thereby increase, instead of lessening the distance, so