On our imaginary switchboard the DIFFUSION switch would not be safe to tamper with. It would be near the SOLUTION switch, and almost as dangerous. For if you were to make diffusion cease in the world, the dissolved food and oxygen in your blood would do no good; it could not get out of the blood vessels or into the cells of your body. You might breathe all you liked, but breathing would not help you; the air could not get through the walls of your lungs into the blood. Plants would begin to wither and droop, although they would not die quite as quickly as animals and fishes and people. But no sap could enter their roots and none could pass from cell to cell. The plants would be as little able to breathe through their leaves as we through our lungs. If gas escaped in the room where you were, you could not smell it even if you stayed alive long enough to try; the gas would rise to the top of the room and stay there. All gases and all liquids would stay as they were, and neither would ever form mixtures. It would not make so much difference in the dead parts of the world if diffusion ceased; the rocks, mountains, earth, and sea would not be changed at all at first. To be sure, the rivers where they flowed into the oceans would make big spaces of saltless water; and when water evaporated from the ocean the vapor would push aside the air and stay in a layer over the ocean, instead of mixing with the air and rising to great heights. But the real disaster would be to living things. All of them would be smothered and starved to death as soon as diffusion ceased. Here is an experiment that shows how gases diffuse: