in its neighborhood the electrical and calorific ethers, and sets them into motions which may be communicated from one to the other, but which are communicated to ponderable matter, or result in mechanical action, only or chiefly by the impulse of the denser or calorific ether. When the sun shines on land and water, as we have already said, there is a violent ethereal commotion in the interstices of the superficial matter, which we will now suppose to be that of the calorific ether; and by virtue of this motion, together with whatever affinities this ether may be supposed to have for ponderable matter, we may account for evaporation, and the production of those vast aërial currents by which the evaporated water is diffused. In the production of aërial currents, heat is converted into force, and hence vapor is converted into watery globules mechanically suspended on clouds, which, by their friction, sweep the electrical ether into excessive condensation in the great Leyden-jar arrangement of the sky. Whatever it may be that gives relief to this condensation, the relief itself consists in motion, either translatory or vibratory, of the electrical ether or ethers. As this motion, if it be such, often takes place through gases, liquids, and solids, without any sensible mechanical effect, and at other times is contemporary with phenomena of intense heat, we may, till otherwise informed, suppose, that, whenever it produces a mechanical effect, it is by so impinging on the calorific ether as to produce the motion of heat, which is instantly thereafter converted into mechanical force. It is not so much the greatness of the amount of this mechanical force which gives it its peculiar destructiveness, as the inequality of its strain; not so much the quantity of matter projected, as the velocity of the blow. One may have his brains blown out by a bullet of air as well as one of lead, if the air only blows hard enough and to one point. Whatever its material, the edge of the thunder-axe is almost infinitely sharp, and its blow is as destructive as it is timeless. But it is always heat, not electrical discharge, which only sometimes causes heat, that strikes the blow.