Eventually almost all of the rain that falls runs into the rivers and lakes and later finds its way into the ocean, where it is again taken up into the air by the sun’s rays. But many other things happen to parts of the rain which do not find their way into the ocean. In the paved street, of course, where the water cannot sink in, it flows into the gutter and thence into the sewer and on down to the river or wherever it is that the sewers are emptied. You see, it depends very much on what the earth’s surface is covered with at the place where the rain falls. When it strikes where there is vegetation a great deal of it stays in the soil at a depth of comparatively few feet. If it is soil where trees and other plants grow a great deal of it is sucked up from the ground by this vegetation and given back into the air through the leaves and flowers. Some of the rain keeps sinking on down into the earth until it strikes some substance like rock or clay, through which it cannot sink, and then it follows along this until it finds something it can get through and collects in a pool and forms an underground lake, and may cause a spring to flow. Then there are also worms and other forms of animal life in the earth which use up some of the water. But it all gets back into the air eventually to come down some time again in the form of rain. Why Does Rain Make the Air Fresh? The main answer to this question must be that the rain in coming down through the air drives the dust and other impurities which are in the air before it, and so cleans the air and makes it absolutely clean. In addition to this it is now stated that since very often rain is produced by electrical changes in the air, and that these electrical changes produce a gas called ozone, which has a delightfully fresh smell, it is this ozone that makes us say the air has become fresh. The air above our cities is almost constantly filled with smoke, containing various poisonous gases, and these are driven away by the falling rain. Then, too, there is always a greater or less accumulation of dirt, garbage and other things in the cities which give off offensive smells constantly, but which we do not notice always because we become used to them. When the rain comes down it washes the streets and destroys these smells, and that makes the air fresh and delightful to take into the lungs. In the country the air is more nearly pure all the time, because the things which spoil the air in the city are not present. Is a Train Harder to Stop Than to Start?