This trick is often used when a message is wanted in answer to a question and cannot be written in advance. The usual method is, however, to hold the slate under the table-top and write on it while it is held there. At first this was done by means of a tiny bit of slate-pencil slipped under the nail of the big finger. Slade soon found that this was suspected, and he made a point of keeping his nails short. The trade which is at the back of mediums then supplied thimbles with bits of pencil attached, which the medium could slip on to his finger as he put the slate under the table. Even thimbles with three differently coloured chalks were made, and the innocent sitter would be invited to select his own colour for the spirits to write in. The most amazing tricks were developed. Robinson tells of a man who would let you bring your own slate and hold it against your own breast, and the message then appeared on it. He "tried" your slate when you brought it by writing on it with his pencil. But, of course, he sponged out all his writing before he handed the slate back to you, as you could see. He had a double pencil--slate at one end and silver nitrate at the other--and what he wrote with the latter was invisible until it was damped with salt-water. Well, the sponging (or damping) had been done with salt-water, and so the message (in silver nitrate) appeared as the slate dried against your breast. When you thus allow the medium to use his own apparatus in his own room you need not be surprised at any result whatever. The sensible man will remember that behind the mediums is the same ingenious industry which supplies conjuring outfits. Mr. Selbit showed Mr. Moseley a typewriter, on an ordinary-looking table, which spelt out, by invisible fingers, a message in reply to your question. There was an electrical mechanism in the table, and an electrician in the next room controlling it by a wire through the hollow table-leg. But even without such elaborate mechanism mediums can baffle quite vigilant sitters. There was one who would allow you to examine his nails, yet he got slate-messages without putting the slate under the table. He had ground slate-pencil to dust, mixed it with gum, and then cut the mixture into little cubes or pellets. He simply stuck these on his trousers, and, _after_ you had examined his nails, helped himself to one.