Fig. 37.
Fig. 38.
Explanation.—One of the candlesticks is hollow, and contains in the upper part, A, some fine sand, which escapes by the hole, B, to run down into the receiver, C. When the latter is full up to D, it runs out by that hole, and falls on the blade of the knife to destroy its equilibrium. As the time of the sand reaching the level of the outlet is regulated by the dimensions of the receptacle, C, its bottom, E, is made movable, and consequently by fixing it at certain points the moment of action can be timed to one, two, or three minutes.
10. The Loaded Knife.—The handle is hollow, and divided into three compartments.
In the section A, is quicksilver, running by a hole, B, into the division, C. So far the knife remains balanced, but when the mercury rises as far as D, it overflows into the part G, when the end being overweighted, the knife must fall.
Fig. 39.
