in the manufacture of carbonic-acid waters, for instance. The air thus incorporated in the water is easily removed by warming the liquid, when infinite numbers of little bubbles may be seen adhering to the walls of the vessel or rising through the midst of the water. But to drive out all the dissolved air, the water should be subjected to a prolonged boiling, and this causes a wonderful increase in its cohesion after it is cooled; and water which has been treated thus will not boil except at temperatures considerably higher than the normal boiling point. Every engineer knows that the water from which he generates steam in his boilers must be aerated, if he would have the machine work regularly and avoid the danger of explosion.
Seeing so much effort displayed without relaxation on the confines of the water and the air in a simple gaseous globule, it is natural to inquire into the enormous sum of work that must be effected without interruption in the surface common to the whole atmosphere and all the rivers, streams, lakes, and seas of the globe; but the most brilliant imagination is confounded in the face of so prodigious an activity.
Who, indeed, shall measure the immense quantity of invisible vapor diffused in the atmosphere? In what balance shall we calculate the weight of the fogs and the clouds suspended above our heads? Who shall weigh the long streams of ice particles floating in the upper regions of the air? Who, in particular, shall adequately estimate the services that are rendered to mankind by those legions of liquid particles that are carried up to great heights in the atmosphere, and distribute warmth and fertility everywhere?
To return to our particles of air penetrating the free surface of the water, what should we see if we fancied everything sufficiently magnified? Gaseous particles gliding one behind another in the intervals of the upper liquid layer; here, particles of the pre-eminently vivifying gas, oxygen, whose mission it is to purify the water and give breath to the inhabitants of rivers and seas; there, molecules of another gas, the mission of which, among other things, is to modify the intensity of the action of its companion; argon, the office of which we hope to find out some day; and molecules of a fourth gas, carbonic acid, which is essential to the growth of plants. But this is not all, for we are further astonished to see penetrate the water infinite numbers of animal and vegetable germs only awaiting favorable conditions to grow and develop with wonderful rapidity. We all know that if water previously boiled be exposed to the light in an open vessel there will form on the sides of the vessel in the course of a week spots in which a powerful microscope will reveal the presence of millions of minute plants associated with legions of animalcules.
