Let us see if we cannot learn something more about the atmosphere. But first of all let me ask, What can you tell me about it?
"You cannot see the air; you can feel it, and often hear it."
Yes, indeed we can. How delightfully fresh it comes to us as we swing, or when we are driving fast, or sailing; and how terrible its force is when the stormy wind rushes past, driving everything before it! It is then we can understand that the gentle air, which yields to the slightest touch, may be a very mighty power indeed.
And now I am going to tell you something about the air which may surprise you. We often say of a thing that it is "as light as air"; but air is not really light, it is so heavy that it would press upon us and crush us, just as a great hammer might crush your little finger, only that this heavy weight of air presses quite evenly everywhere all through our body, within and without, upward as well as downward, and yields at once when we move, so that we do not feel its weight.
Just think of the weight of water which lies above a little fish as it swims far down in the sea. Why is it not crushed by it? Just for the same reason; the water is all round the fish, as the air in our ocean is all round us; and it presses so evenly that it cannot be felt in any particular part.
Another very wonderful thing about the atmosphere is that what we call the air is made up of two airs, or gases, as different as possible from each other, but mixed so as to make exactly that particular sort of air which is fit for us to breathe.
One of these gases, named oxygen, might well be called "life-sustainer"; it forms about one-fifth of the air we breathe, and is that part of it which makes our fires burn and our lamps give light, and keeps us and all the animals alive. The other gas is called nitrogen; it is a dull gas, with no life in it, and remains behind when all the oxygen is taken out of the air. But this part of the air is very useful; it prevents the breathing of men and animals and the burning of fires and lamps, from going on too fast. If you had only the life-sustaining part of the air to breathe, you would soon die; and if the air was all made of that part which burns so well, one spark falling upon it would be enough to burn up the whole world, for no one could put the fire out.
These two gases are mixed in nearly the same proportions in all climates so as to make the beautiful pure air which God has given us to live and go about in. There is another gas, called carbonic acid, made partly of oxygen and partly of carbon, or burnt wood, which might be called "life-destroyer," for it will put out light and make an end of life. It is one of the most deadly poisons, and forms the "choke-damp" which too often suffocates the miner; but what we call fresh air contains such a very small proportion of this dangerous gas that it is harmless. Still we must remember that every time anyone or any animal breathes, some of the air by which we live is taken away from that which surrounds us, and some of this poisonous air is thrown into it. If this is the case, should we not, by degrees, find the air becoming less and less pure and fit for us to breathe?
Certainly it would be so, if God had not made a beautiful provision for keeping the air fresh, which I will try to explain to you.
You may remember that the Lord Jesus, after He had made the five barley loaves and two small fishes prove enough for thousands of hungry men and women and little children, turned to His disciples, and said, "Gather up the fragments that remain, that nothing be lost." So, in the world around us, we may often see that God gives freely, but does not allow what He has freely given to be lost or wasted.