How shot are round.
Whenever there is a little of any liquid by itself, it tends to take a round shape, as seen in the quicksilver, and in the drops of water on windows and leaves. We see a pretty example of this in the manufacture of shot. Perhaps you have seen a shot tower. It is very high. All the shot that are made drop from the top to the bottom. At the top they have the melted lead. They pour it into a sort of cullender—that is, a vessel with holes in it. These holes are quite small. From each one of these holes come out, one after another, drops of the melted lead. Each drop is round. It cools as it goes down all this long distance in the air, and by the time that it gets to the bottom of the tower, it is cold and solid. The shot all fall into a tub of water, so that they may keep their round shape.
Now why is it that the shot are round? Simply because when they begin to fall they are melted lead—that is, a fluid. Their particles are disposed, therefore, to hold together in a round form, like the particles of quicksilver, or of a drop of water.
Bullets.
Bullets are made by pouring the melted lead into moulds. Think, now, why they can not be made in the same way that shot are. The reason is that there are more particles in a bullet than can hold together in a round shape while the lead is fluid. You can not have very large drops of any fluid. The particles will hold together only in small companies.
Making soap-bubbles roll.
There is one thing that you can do with soap-bubbles which perhaps you have never thought of. You can make them roll on a table or on the floor by blowing them along. The reason is that the particles of soap and water mixed together hold on to each other, or attract each other, better than the particles of water alone.
Questions.—What is the great difference between a solid and a fluid? Give the comparison about a crowd. Do we know what it is that fastens the particles of a solid together? What is it called? What is said about the particles being near together? Tell about the experiment with the India-rubber and the lead. How do liquids differ from solids in attraction? Why is water on a pane of glass often in drops? Why is it that you can spoil a drop by a touch? Tell how a shot differs from a drop of water. Is the attraction between the particles alike in all fluids? Tell about the quicksilver. Tell about the drops of water on leaves. Tell about oil dropped upon water. How is it with oil spilled upon cloth or wood? Describe shot-making. Why are the shot round? How are bullets made? Why can not they be made in the same way that shot are? What is said about soap-bubbles?