hydrogen, but we have not yet explained the phenomena which attend its combustion. This gas when pure burns with a very pale flame, the product of its combustion being water, which escapes into the atmosphere in the form of an invisible vapour. If a cool tumbler be inverted over the flame this vapour will be condensed into minute drops, which will trickle down the inner surface of the glass. The combustion of hydrogen is therefore a manifestation of the intense affinity of this gas for the oxygen of the air.
If we mix the two gases in the proportion in which they combine to form water, and apply a lighted match to the mixture, the gases will instantly unite with a deafening explosion. All the water produced will merely suffice to damp the surface of the vessel in which the .explosion takes place, as no less than 2550 measures of the gaseous mixture are required to form one measure of water.
Here is another marvellous revelation! The two gases have separately resisted every attempt made by the joint efforts of cold and pressure to liquify them, yet they combine and form water, the type of liquidity!
According to the dogma of the Four Elements, everything that is neither fire, air, nor water, is necessarily earth. Now a moment's consideration will convince us that innumerable bodies having the most diverse properties are comprised in this definition of the so-called element.
