The experiments which we give this week are both performed with an apparatus found in almost every house, namely, a tobacco pipe. Simple as this little article of luxury is to too many, it will serve for many purposes of amusement besides the special one for which it is designed ; two of its uses we will now describe. Take an allspice, or a pea is better, and through its center thrust a pin or needle, so that there shall be an almost equal weight of metal on each side ; then place one end of the pin in the stem of a tobacco pipe, and applying the lips to the bowl, blow gently, when the pin and allspice will dance in the air in a very amusing manner. You may not succeed the first few times, but as soon as you have learned to keep the pipe quite steady, and to give a continuous current of air, you will be able to make the pin and allspice dance for a considerable time. The bowl of the pipe forms a receptacle for condensing the air, and acts like the equalizing chamber of a force pump, by which continual pressure is exerted, and a stream of air passes through the stem to the orifice at the mouth of the pipe ; here meeting with the allspice, it blows it up a little way, and then the allspice falling again by its own gravity, is met by another jet of air, and so is kept dancing up and down. "But," we are asked, " why does it not tumble away from the pipe, and not meet the next jet of air ?" Because, when the air issues from the pipe it has a ten- dency to spread itself out, and so forms a kind of cushion, gradually increasing in dimensions and diminishing in power ; and besides, if it is blown up straight, it will be sure to take the nearest way to the ground from the point where it stops going up, and that is always a straight line ; but if you blow it out at an angle, it will surely fall to the ground, as you will probably find out during your experiments. The next illustration shows a simple way of making illuminating gas by means of the same apparatus—a tobacco pipe. .Bituminous coal contains a number of chemical compounds, nearly all of which can, by distillation, be converted into an illuminating gas ; und with this gas nearly all our cities are now lighted in the dark hours of night. To make it as represented in our engraving, obtain some coal dust, (or walnut or butternut meats will answer,) and fill the bowl of a pipe with it ; then cement the top over with some clay, place the bowl in the fire, and soon smoke will be seen issuing from the end of the stem ; when that has ceased coming, apply a light, aa it will burn brilliantly for several min- utes; after it has ceased, take the pipe from the fire and let it cool, then remove the clay, and a piece of coke will be found inside ; this is the excess of carbon over the hydrogen con- tained in the coal, for all the hydrogen will combine with carbon at a high temperature, and make what are called hydro-carbons—a series of substances containing both these olemental forms of matter.