Why is the water in some springs warmer than in others? In springs where the water is warm, the streams flowing into them are so near the surface of the earth as to be warmed by the sun, while in springs where the water is colder, the streams are much deeper in the earth. What becomes of the water in the springs? It runs away down the valleys, forming _brooks_ and _creeks_. When these brooks and creeks flow into other brooks and creeks, what do they form? They form _lakes_ and _rivers_. Into what do the rivers flow? The rivers flow into the ocean. How are waves produced? Waves are produced by the winds blowing against the surface of the water. What does a light wind produce? A light wind produces only ripples on the surface of the water. What does a stronger wind produce? A stronger wind produces waves in the water. Why is the water of the ocean and the larger lakes seldom at rest? Because the wind touching the water seldom ceases to blow. To what depth does the wind disturb the water of the ocean? Wind seldom disturbs the ocean to a greater depth than thirty feet below its surface. Fogs and Clouds. What is always taking place from the surface of the water in the rivers, lakes, and oceans? The water is always passing off in the form of vapor. Where does this vapor go? It goes into the air so that the air becomes filled with moisture. What kind of air will hold the most vapor? Warm air will hold the most vapor. When warm air becomes colder, what is done with the vapor? The vapor is condensed into small particles of water. When this takes place near the earth, what does it produce? It produces a _fog_. Where do fogs mostly occur? Fogs mostly occur over low grounds and along the course of streams. When the vapor is condensed higher up in the air, what does it produce? It produces a _cloud_. What is a cloud? A cloud is only a fog, higher up in the air. Do fogs ever ascend in the air? Yes; they often ascend, and thus produce clouds. What causes the vapor of the air to be condensed into clouds? Cold causes it to be condensed into clouds. Does the air grow colder as we ascend? Yes; the higher we ascend, the colder we find the atmosphere. What becomes of the vapor in the air, as it ascends from the earth? The vapor is condensed into clouds in the upper regions of the air. Why do we mostly see clouds at the top of a mountain? Because the vapor in the air is condensed into clouds by the cold at the top of the mountain. When is a cloud formed in the air? When a warm, damp wind meets with a cold wind, its vapor is condensed and a cloud is formed. Are clouds often formed in this way? Yes; clouds are often quickly formed in this way. When the cloud passes into a warmer current of air, what becomes of it? It is changed back into vapor, so that it cannot be seen. How then can a cloud in the sky disappear very quickly?