Experiments on combustion might be multiplied almost to any amount, but the above will be sufficient for the present. When we come to treat of the properties of the gases and some other substances, we shall have occasion to recur to this subject.
The production of caloric by chemical combination may be exhibited by mixing carefully one part of oil of vitriol with two of water, when sufficient heat will be produced to boil some water in a thin and narrow tube, which may be used as a rod to stir the mixture.
The production of heat by electric and galvanic agency belongs to another subject. I will content myself with saying here, that these forces afford the most powerful aid in decomposing and uniting various bodies, and that it was by the immense power of a battery of 2,000 pairs of plates, belonging to the Royal Institution in London, that Sir H. Davy discovered the metallic bases of the alkalies and earths.
HYDRAULICS.
The science of Hydraulics comprehends the laws which regulate non-elastic fluids in motion, and especially water, &c.
Water can only be set in motion by two causes—the pressure of the atmosphere, or its own gravity. The principal law concerning fluids is, that they always preserve their own level. Hence water can be distributed over a town from any reservoir that is higher than the houses to be supplied; and the same principle will enable us to form fountains in a garden, or other place. Should any of our young friends wish to form a fountain, or jet d’eau, they may, by bringing a pipe from T, a water-tank, which should be at the upper part of the house, convey the water down to the garden. Then by leading it through the earth, underneath the path or grass-plot, and turning it to a perpendicular position, the water will spring out, and rise nearly as high as the level of that in the tank. The part of the pipe at B should have a turnkey, so that the water may be let on or shut off at pleasure.
THE SYPHON.
