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in the model above deſcribed: for, when lodged in their reſpective cells, they are upheld, like the levers, by the elaſtic power of the ſprings on which they reſt; till a preſſure ſuperior to that power is applied;—and are again reſtored to their ſtations by the reaction of the ſprings, when the weight, which depreſſed them, is withdrawn. Each ſlider projects its ſide B (as appears in the fifth figure) beyond the ſpherical ſurface of the barrel, or frame, which contains it; as the extreme points of the levers (in the above model,) are projected beyond the curved frame, in which they move. The point C is projected through the interior groove, into the ſpace which forms the center, or key-hole, expreſſed on the flat ſurface A.—When the key, therefore (which the fourth figure repreſents,) is applied, it muſt of courſe encounter theſe interior projections; and when preſſed forward, (the ſpaces indented on its point being unequal,) will force the ſliders
