jet, sulphur), their action is impeded by the interposition of a body (as paper, leaves, glass, or the like) when that way is impeded and obstructed, so that that which exhales cannot reach the corpuscle to be allured. Terrestrial and magnetick coition and motion, when corporeal impediments are interposed, is demonstrated also by the efficiencies of other chief bodies due to their primary form. The moon (more than all the stars) agrees with internal parts of the earth on account of its nearness and similarity in form. The moon produces the movements of the waters and the tides of the sea; twice it fills up the shores and empties them whilst it moves from a certain definite point in the sky back to the same point in a daily revolution. This motion of the waters is incited and the seas rise and fall no less when the moon is below the horizon and in the lowest part of the heavens, than if it had been raised at a height above the horizon. So the whole mass of the earth interposed does not resist the action of the moon, when it is below the earth; but the seas bordering on our shores, in certain positions of the sky when it is below the horizon, are kept in motion, and likewise stirred by its power (though they are not struck by its rays nor illuminated by its light), rise, come up with great force, and recede. But about the reason of the tides anon; here let it suffice to have merely touched the threshold of the question. In like manner nothing on the earth can be hidden from the magnetick disposition of the earth or of the stone, and all magnetical bodies are reduced to order by the dominant form of the earth, and loadstone and iron show sympathy with a loadstone though solid bodies be interposed.
CHAP. XVII.
On the Iron Cap of a Loadstone, with which
it is armed at the pole (for the sake of the
virtue) and on the efficacy of the same.
onceive a small round plate, concave in shape, of the breadth of a digit to be applied to the convex polar surface of a loadstone and skilfully attached; or a piece of iron shaped like an acorn, rising from the base into an obtuse cone, hollowed out a little and fitted to the surface of the stone, to be tied to the loadstone. Let the iron be the best steel, smoothed, shining, and even. A loadstone with such an appliance, which before only bore four ounces of iron, will now raise twelve. But the greatest force of a combining or rather united nature is seen when
