George Gamblin, age 11, of Oromocto, N.B., for his question!

What is in the air?

The air itself is made of gases and each particle of gas is no bigger than a molecule. In a thimbleful of air it is estimated that there are more than 100 million million of these gas molecules and each one of then has plenty of room to dash around.

Even so, there are plenty of other little things in the world which are not much bigger than single molecules. Some of these tiny fragments are light enough to float around with the gases of the air. For this reason, no air is absolutely pure.

There are fragments of salt which get into the air from the splashing waves of the ocean. There are tiny spores which ride the breezes, They come from mushrooms, puffballs, mosses, molds, mildews and a host of other spore‑making plants.

Sufferers from hay fever know that their sniffles come from pollen in the air. Pollen grains come in all shapes. Perhaps you wonder where smoke disappears. It too becomes tiny fragments mixed with the air. Tons of smoke and soot from countless fires and furnaces are added to the air every day,

The largest amount of material afloat in the air, however, is dust, Every solid object in the world is busy wearing away. A particle rubs off here, a fragment chips off there. These particles become dust and dust blows up from the soil, from buildings, from everything else you can mention And much of it is lifted aloft by the breezes and mixes with the air,

Samples of these various objects are present in the air all over the world. Dust, pollen, soot and. salt are present in the air miles above the clean oceans. Why isn't the air bogged down with all these free riders? The nnswar is that sooner or later all those flying fragments must come to rest.

Dust, as you know, is always settling on every surface indoors and out. Along with it are particles of soot and  more spores hoping for a suitable spot on which to grow and pollen hoping to land on a certain flower. More dust is washed down with the rain, Salt in the air also falls with the rain. These fragments often help form rain drops.

Tons of these dusty fragments fall every day and tons more take to the air to replace them. Meantime the mixture of air gases remains the same. This mixture is 79 per cent nitrogen and 21 per cent oxygen, The remaining one per cent is composed of carbon dioxide, hydrogen, neon, krypton, helium, ozone and xenon.

Also present in the air in varying amounts is water vapor, which is a gas. This is evaporated from water surfaces below. For a time it becomes mist and rides the breezes as clouds. But sooner or later, the clouds become rain, snow or hail. Water vapor, like the dust, is returned to the earth.