These stories of useful inventions are chapters in the history of civilization and this little book is a book of history. Now we are told by Herodotus, one of the oldest and greatest of historians, that when the writer of history records an event he should state the _time_ and the _place_ of its happening. In some kinds of history--in the history of the world's wars, for example, or in the history of its politics--this is strictly true. When we are reading of the battle of Bunker Hill we should be told precisely when and where the battle was fought, and in an account of the Declaration of Independence the time and place of the declaration should be given. But in the history of inventions we cannot always be precise as to dates and places. Of course it cannot be told when the first plow or the first loom or the first clock was made. Inventions like these had their origin far back in the earliest ages when there was no such person as a historian. And when we come to the history of inventions in more recent times the historian is still sometimes unable to discover the precise time and place of an invention. It is in the nature of things that the origin of an invention should be surrounded by uncertainty and doubt. An invention, as we shall see presently, is nearly always a response to a certain want. The world wants something and it promises a rich reward to one who will furnish the desired thing. The inventor, recognizing the want, sets to work to make the thing, but he conducts his experiments in secret, for the reason that he does not want another to steal his ideas and get ahead of him. We can see that this is true in respect to the flying machine. The first experiments with the flying machine were conducted in secret in out of the way places and pains were taken that the public should know as little as possible about the new machine and about the results of the experiments. The history of the flying machine will of course have to be written, but because of the secrecy and mystery which surrounded the beginnings of the invention it will be extremely difficult for the future historian to tell precisely when the first flying machine was invented or to name the inventor. If it is so difficult to get the facts as to the origin of an invention in our own time, how much more difficult it is to clear away the mystery and doubt which surround the beginnings of an invention in an age long past!