There is an ingenious double form of this flap slate with which it is possible to make a message appear on both inside surfaces of a pair of locked slates without having them leave the sight of the sitter for an instant. The two slates are hinged together like the old-fashioned school slates but with the hinges on the outside of the slates. The slabs of slate are very thin and the ends of the frames bevel toward them slightly. One end of each frame is so made that by pressing on one of the hinge screws the frame end is released and can be drawn out about a quarter of an inch. A very thin slab of slate called the “flap” is arranged to fit snugly over the real slate when the frame ends are in place but drops out as soon as they are released and drawn out. In working these slates the medium writes a message on the inside of one of them, say the left, and also on one side of the flap. The end of the slate with the message is then drawn out and the flap inserted, message side down, and the frame fastened back in place. A secret mark on the outside of the frame shows which slate is written upon. The slates can then be shown and will appear clean on all four sides, and it is possible to either seal or lock them without interfering with the success of the demonstration. They are then placed on the table with the fake ends nearest the medium and while he leans on their ends with half-folded arms, engaging the sitter in conversation, he at the same time with the fingers of his concealed hand pulls out the frame ends, allowing the flap to fall from one slate to the other, and then secures it in place by putting the ends back. Of course when the slates are opened a closely written message is found on both. Another sort of double slate intended for producing a similar effect in dark seances or cabinet work also has a loose end which instead of moving a quarter of an inch draws out to any length, bringing the slab with it. After the lights are out or the cabinet closed it is an easy matter to draw out the slab and write a message on it. [Illustration: WRITING ON “HONEST SLATES” BY MEANS OF WEDGE AND WIRE.] Writing is sometimes produced between two perfectly honest slates which have been fastened together at the corners by inserting a wedge of hard wood between the frames, thus separating them enough to slip between them a piece of wire with a bit of slate pencil fastened to its tip. By this means a message can be produced at a dark seance in a few minutes without breaking the seals. There is a form of slate where the slab is invisibly hinged on the side so that it opens like a door and is held shut by a secret catch. This slate can be used in a dark seance or under the table at a light one. It can also be used on a cloth-top table with an invisible trap. The trap and the hinged slate drop down together and the medium is able to write on the slate by reaching under the table.