In order to make this extraordinary and entertaining experiment, you must provide yourself with a glass, having a large foot, the basis of this glass is to terminate in a point, as the annexed figure shews. [Illustration] Put in the glass an ounce of spirits of nitre, well rarified; then pour over it an ounce of essential oil of guaiacum. This mixture will produce a very considerable ferment, attended with smoak, out of which there will rise, in the space of three minutes, a spungy body, resembling perfectly a common mushroom. This spungy substance, formed by the fat and oily particles of the guaiacum wood, being drawn up by the air, covers itself with a very thin coat of the matter that composes the oil of guaiacum. CHAP. XXX. _To make a Ring shift from one Hand to another, and to make it go on whatever Finger is required on the other Hand, while somebody holds both your Arms, in order to prevent any Communication between them._ Desire some person in the company to lend you a gold ring, recommending him at the same time to make a mark on it that he may know it again. Have a gold ring of your own, which you are to fasten by a small cat-gut string to a watch barrel, which must be sown to the left sleeve of your coat. Take in your right hand the ring that will be given to you; then taking with dexterity near the entrance of your sleeve the other ring fastened to the watch barrel, draw it to the fingers ends of your left hand, taking care nobody perceives it: during this operation, hide between the fingers of your right hand the ring that has been lent to you, and hang it dexterously on a little hook sewed on purpose on your waistcoat near your hip, and hid by your coat; you will after that shew your ring which you hold in your left hand; then ask the company on which finger of the other hand they wish it to pass. During this interval, and as soon as the answer has been given, put the before-mentioned finger on the little hook, in order to slip on it the ring; at the same moment let go the other ring, by opening your fingers: the spring which is in the watch barrel, not being confined any longer, will contract, and make the ring slip under the sleeve, without any body perceiving it, not even those who hold your arms, as their only attention being to prevent your hands from communicating, they will let you make the necessary motions. These motions must be very quick, and always accompanied by stamping with your foot. After this operation, shew the assembly that the ring is come on the other hand: make them remark well that it is the same that had been lent you, or that the mark is right. Much quickness and dexterity must be made use of to succeed in this entertaining trick, that the deception may not be suspected. CHAP. XXXI. _To guess, by smelling, which has been the Number struck out by a Person in the Company, in the Product of a Multiplication given him to do._