XI. EXAMPLES OF PRE-HISTORIC DRAWINGS 135 XII. LAKE-DWELLINGS 148 XIII. THE GUADALOUPE HUMAN FOSSIL 159 THE PUZZLE OF LIFE. _THE FRAMEWORK OF THE PUZZLE._ You must often have looked with wondering eyes at this World of ours, and asked yourselves questions about it. How did it come here? What is it made of? How old is it? All of them questions not to be answered without a great deal of thought and study, and even then not so perfectly as we should like. It is easy to say “It is here,” and “It is made of earth,” and “It surely must be old,” but that will not satisfy us. We want to know something more certain than this, if possible. We can see that a clock goes with wheels, but we are not very intelligent people if we do not want to find out what makes the clock go. One way of finding out is to pull things to pieces, but we cannot exactly do this with the World. We must think about it, and put together all the knowledge we can gain from the outside and inside, and from the other Worlds around us, which we can see, and when we have done this we may get something like answers to our questions. How did it come here? But this is not quite the right way of asking the question, because the World is never for two moments together in the same place. It is travelling in a great circle round the Sun at the rate of more than sixty thousand miles an hour, and has been ever since it was formed. That is a wonderful arrangement by which all Worlds travel round some other World larger than themselves, in greater or less circles, and we do not know why it is, though we are certain that it is so. The Moon travels round us once in about every month, and we and the Moon together round the Sun once in every year. Then again, other planets, with their moons, such as Jupiter, for instance, travel round the Sun in much larger circles than our World, and take many years to do the journey, while Venus, which is nearer the Sun than we are, travels in a much smaller circle, and takes less time. We do not perceive that we are moving so fast because everything we see is moving equally fast with us; but there is no doubt that we are spinning along at sixty thousand miles an hour.