I have seen a medium use the double or folding slate and get rid of the false flap in this way: He used a pair of small slates. These he opened out with the flat side towards the audience, and while in his hand, cleaned those two sides away from the table. He now showed the reverse sides and cleaned them likewise. He now closed the slates, but toward him, instead of away from him, holding them close to his body, and as he does so, the false flap, by this movement, slips easily and unperceived beneath his coat or vest. I once witnessed a test which, for a time, completely nonplussed me, but, after considerable study and experimenting, I solved it. This is the effect of the test: A person was allowed to bring two slates; he was to wash them himself and securely seal them in the presence of the medium, the medium placing, before the slates were sealed, a piece of chalk between them. The slates were sealed after this fashion: Around the whole length and width of the slates court plaster was stuck, and that was also sealed to the slates with sealing wax, making it an utter impossibility to insert a piece of wire, or like substance, between the slates. Nevertheless, the slates were held under the table and presently removed, unsealed, and writing in a very poor hand found upon the inner surface of one of the slates. It could hardly be called writing, being hardly more than a scrawl. Now, how can this be accounted for? By one of the simplest devices imaginable. The medium placed the piece of chalk between the slates. This was composed of pulverized chalk, mixed with a little water, glue and iron filings, and allowed to become hard. The medium, while under cover of the table, traced with a magnet below the slate the words found upon the inside, but backward, the same as type is set for printing; if not, the writing on the slate will be in reverse. The chalk, on account of the iron filings it contains, follows the direction of the magnet. (Fig. 13.) [Illustration: Fig. 13.--Magnetic Writing.] We now come to another idea with two slates. Have two slates made with fairly deep wooden frames, deep enough to hold the slate proper and a false flap of slate. One made of silicate book-slate stuff is preferable. Your apparatus consists now of two slates and one false flap. The false flap is made to fit very tightly, so it will not fall out of its own weight. The slates in the frame also fit snugly. The frames are mortised out a little thicker than the slate, say twice as thick. This allows the slate to work backward and forward, from front to back, and _vice versa_. If the slate is well pushed down and the flap placed on it, the flap will not fall out, but if you press the slate on the back forward, it shoves out the flap, and if it is covered with the other or second slate during this operation, it is forced into the second slate, which holds it firm and secure. [Illustration: Fig. 14.--The Thimble Carrying False Key and Chalks.]