To make a mutual Exchange of the Liquor in two Bottles, without using any other Vessel.
Take two bottles, which are as nearly equal as possible, both in neck and belly, and let one be filled with oil, and the other with water; then clap the one that is full of water dexterously upon the other, so that the two necks shall exactly fit each other; and as the water is heavier than the oil, it will naturally descend into the lower bottle, and make the oil ascend into its place. In order to invert the bottle of water without spilling the contents, place a bit of thin writing paper over the mouth of the bottle; and when you have placed the bottle in the proper position, draw out the paper quickly and steadily.
How to make a Peg that will exactly fit Three different Holes.
Let one of the holes be circular, the other square, and the third an oval; then it is evident, that any cylindrical body, of a proper size, may be made to pass through the first hole perpendicularly; and if its length be just equal to its diameter, it may be passed horizontally through the second, or square hole; also, if the breadth of the oval be made equal to the diameter of the base of the cylinder, and its longest diameter equal to the diagonal of it, the cylinder, being put in obliquely, will fill it as exactly as any of the former.
To place Three Sticks, or Tobacco Pipes, upon a Table, in such a manner that they may appear to be unsupported by any thing but themselves.
Take one of the sticks, or pipes, (see Plate,) AB, fig. 2, and place it in an oblique position, with one of its ends, B, resting on the table; then put one of the other sticks, as CD, across this in such a manner that one end of it, D, may be raised, and the other touch the table at C. Having done this, take the third stick E, and complete the triangle with it, making one of its ends E rest on the table, and running it under the second, CD, in such a manner that it may rest upon the first, AB; then will the three sticks, thus placed, mutually support each other; and even if a small weight be laid upon them, it will not make them fall, but strengthen, and keep them firmer in their position.
How to prevent a heavy Body from falling, by adding another heavier Body to it on that side towards which it inclines.
On the edge of a shelf, or table, or any other horizontal surface, lay a key, (see Plate,) CD, fig. 3, in such a manner, that, being left to itself, it would fall to the ground; then, in order to prevent this, take a crooked stick DFG, with a weight, H, at the end of it; and having inserted one end of the stick in the open part of the key, at D, let it be so placed, that the weight H may fall perpendicularly under the edge of the table, and the body by these means will be effectually prevented from falling.
The same thing may be done by hanging a weight at the end of a tobacco-pipe, a stick, or any other body; the best means of accomplishing which will be easily known by a few trials.
To make a false Balance, that shall appear perfectly just when empty, or when loaded with unequal Weights.