Almost everything we have or use had to be invented. Doorbells, telephones, stoves, lamps, refrigerators, printing presses, farm machinery, tools, dynamite, glass, steel—this is only the beginning of a list that could be made many pages long. Of course, air and water and grass and trees did not have to be invented. But inventions fan air into our buildings, pump water to where it is needed, and help in planting grass and trees and taking care of them. Food did not have to be invented, either. But our cavemen ancestors would probably have starved to death if they had not invented weapons for killing wild animals to eat. And certainly the land of the world could not possibly produce enough food for all the millions of people on it now if machines had not been invented for tilling the soil.

   Some very important inventions were made long before any records were kept— long before anyone knew how to write. The knife, the spear, the bow and arrow, ways of making fire, and ways of making cloth and pottery are a few of them. No one has any idea who the inventors of these things were. Even with modern inventions it is not always easy to name the inventor. One person puts on the final touch, but his work is based on the work of many others. It is not possible, for instance, to name one inventor for the automobile. Early automobiles were developed by putting together many inventions.

   In some cases two inventors have invented almost the same thing at almost the same time, even though neither one knew anything about the work of the other. There is an old saying, "Necessity is the mother of invention." It is a good saying. When there is a need for some new device, many people work on it and sooner or later one of them has an idea that turns out to be good. Perhaps more than one person may have the same idea at almost the same time.

   Almost every invention is promptly improved. Edison invented the electric light bulb. But those we use now are not much like Edison's invention. Bell invented the telephone. But many people, if they could see his first telephone, would not know what it was.