To make any Pen-knife out of three jump out of a Goblet, agreeable to the Option of the Company.

Take a silver goblet, as, on account of its opacity, it will hide the means you will employ to make the pen-knife jump out at the desire of the assembly.

This operation consists in a small spring, about an inch broad, by two inches and a quarter long.

You are to take care to subject or bend this spring before you begin the trick with a little bit of sugar, which being compressed between the two ends of the spring, will prevent it from unbending.

Then ask the company, shewing your three pen-knives of different colours, which of them they chuse to see jump out of the goblet.

Put afterwards your three pen-knives in the goblet, taking care to lay the end of the handle of the chosen pen-knife in a little round hole that is in the upper end of the spring, confined by the bit of sugar; and before you withdraw your hand from the goblet, which must contain in the bottom some drops of water, take a little of it with the tip of your finger, and put it dexterously on the sugar, which by melting will leave the spring at liberty to extend and make the pen-knife jump out.

While the sugar is melting, you may stand far from the goblet, and command the pen-knife to jump out; and this will be done to the great astonishment of the spectators. Yet nothing is so simple as the means to make this experiment succeed, without the least assistance from any confederate.

N. B. These little springs, fit for use, may be had of Mr. Pinetti, Hay-Market.