will be a block of ice. Nay, more; when by such mechanical means subdivision can be carried no further, we may resort to a gentle heat and find these microscopic blocks crumbling into fragments finer still; for what is melting but a process of division? In it, particles simply fall apart because the ties of cohesion are sundered by the heat, and the liquid is the same substance, differing from the impalpable powder only in the mobility due to its finer state of division. Now touch the liquid with a somewhat intenser heat. We find that the water is converted into steam, becoming invisible, and that the water-gas occupies a volume seventeen hundred times larger than did the water which it represents. However remarkable this change, yet it does not touch that which gives character to the substance. In all its essential properties it is water still. Furthermore, not the slightest addition or subtraction has been made. The process, in all its steps, from the original block of ice to the seventeen-hundred-fold volume of invisible vapor, is simply a process of division.
Now endeavor to carry the subdivision further. It may be that a fiercer heat will be a keener edge to cleave the invisible particles of water-gas. Thanks to Professor Chandler, who has taught us how to apply the requisite heat without at the time introducing a chemical attraction, so that we may be left confident that, whatever the result, it is accomplished by the same agents by which our previous subdivisions have been made.
In this experiment the steam is passed into a platinum flask, which is kept red-hot. From this flask a delivery tube conveys it to a jar designed to receive the products of the experiment. The invisible steam enters the platinum flask; an invisible gas also passes onward to be caught in the receiver; but afterward, on bringing a flame to the mouth of this receiver, an explosion declares that its contents are water-gas no longer—that a mixture of hydrogen and oxygen has taken its place. The steam particles are evidently broken by the heat. But mark the result: the fragments are no longer particles of water. The red heat has dissected the steam particles, and revealed the fact that they consist of still smaller pieces of hydrogen and oxygen.
In the form of steam, therefore, water is in its finest possible state of division, for to divide it further is to compel it to cease to exist as water. We are therefore entitled to declare that this substance consists of ultimate particles, which can not be divided without changing them into other kinds of matter. These are its molecules. Next, in the light of chemical synthesis, also, we may see the existence of these ultimate particles.
Hydrogen and oxygen are the inevitable constituents of water, and two volumes of hydrogen to one volume of oxygen are the invariable proportions. No human agency can obtain water by combining any other elements, nor by combining these in any other proportions.
These are facts confirmed by all experience. Nevertheless, it mat-
