This, as we have said, is the most simple form of the key, or correspondent. It is a modification of that shown at figure 11. The following figure, 21, represents a key, where the lever is taken advantage of to make a more perfect connection, with less application of power. A key of the above form has been used during the past winter for reporting the proceedings of Congress, and has been found to operate with ease, with certainty, and with great rapidity. A A is the block or table to which the parts are secured. E represents the anvil block. J the anvil, screwed into the block, both of brass. B is another block, for the stop anvil, K, and the standard for the axis of the lever C. L is the hammer, and is screwed into the lever, projecting downward at V, almost in contact with the anvil, J. R is another screw of the same kind, but in contact with the anvil, K, when the lever C is not pressed upon. Under the head of each of these two screws, are tightening screws, which permanently secure the two hammers, to any adjusted position required for the easy manipulation of the lever, C. D is a spring which sustains the arm of the key up, preventing the hammer, L, from making contact with the anvil, J, when not in use. G is a screw connecting with the brass block, B, and F a screw connecting with the block, E. To these screws the two wires, I and H, of the battery are connected. Now, in order to put it in operation, it is necessary to bring the hammer, V, in contact with the anvil, J, for so long a time, and at such regular intervals as are required by the particular letters of the communication. When the key is pressed down, the fluid passes from the battery to the wire, H, then to the screw, G, then to the block, B, then to the lever, C, at the axis, S, then to its metallic anvil, J, then to its screw, F, then to the wire, I, and so to the battery. [Illustration: FIG. 21.] _The circuit of the Electro Magnet, closed and broken by the movement of the lever itself, acted upon by the Electro Magnet. Showing the rapidity with which it is possible to close and break the circuit._