THE FORCES IN AN AIR BUBBLE. 677 



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 en- 

 gineer 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 con- 

 fines 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 cal- 

 culate the weight of the fogs and the clouds suspended above our 

 heads ?. Who shall weigh the long streams of ice particles float- 

 ing 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 suffi- 

 ciently 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 com- 

 panion ; 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 mil- 

 lions of minute plants associated with legions of animalcules. 



