But the age of machinery was coming on. Once in a while there were glimpses of more powerful and complicated devices to be seen among these simple arms.

A new weapon now came about through warfare. Man has been a savage fighting animal through pretty much all his history, but while he tried to kill the other fellow, he objected to being killed himself.

Therefore he took to wearing armor. During the Middle Ages he piled on more and more, until at last one of the knights could hardly walk, and it took a strong horse to carry him. When such a one fell, he went over with a crash like a tin-peddler's wagon, and had to be picked up again by some of his men. Such armor would turn most of the arrows. Hence invention got at work again and produced the cross-bow and its bolt. We have already learned how the tough skin of animals brought about the bow; now we see that man's artificial iron skin caused the invention of the cross-bow.