What was the cross-bow? It was the first real hand-shooting machine. It was another big step toward the day of the rifle. The idea was simple enough. Wooden bows had already been made as strong as the strongest man could pull, and they wished for still stronger ones--steel ones. How could they pull them? At first they mounted them upon a wooden frame and rested one end on the shoulder for a brace. Then they took to pressing the other end against the ground, and using both hands. Next, it was a bright idea to put a stirrup on this end, in order to hold it with the foot. Still they were not satisfied. “Stronger, stronger!” they clamored; “give us bows which will kill the enemy farther away than he can shoot at us! If we cannot set such bows with both arms let us try our backs!” So they fastened “belt-claws” to their stout girdles and tugged the bow strings into place with their back and leg muscles. “Stronger, stronger again, for now the enemy has learned to use belt-claws and he can shoot as far as we. Let us try mechanics!” So they attached levers, pulleys, ratchets and windlasses, until at last they reached the size of the great siege cross-bows, weighing eighteen pounds. These sometimes needed a force of twelve hundred pounds to draw back the string to its catch, but how they could shoot! And Now for Chemistry. Human muscle seemed to have reached its limit, mechanics seemed to have reached its limit, but still the world clamored, “Stronger, stronger! How shall we kill our enemy farther away than he can kill us?” For answer, man unlocked one of the secrets of Nature and took out a terrible force. It was a force of chemistry. [Illustration: DEER-STALKING WITH THE CROSS-BOW This compact arm with its small bolt and great power was popular with many sportsmen.] Who first discovered the power of gunpowder? Probably the Chinese, although all authorities do not agree. Strange, is it not, that a race still using cross-bows in its army should have known of explosives long before the Christian Era, and perhaps as far back as the time of Moses? Here is a passage from their ancient Gentoo Code of Laws: “The magistrate shall not make war with any deceitful machine, or with poisoned weapons, or with cannons or guns, or any kind of firearms.” But China might as well have been Mars before the age of travel. Our civilization had to work out the problem for itself. Playing with Fire. It all began through playing with fire. It was desired to throw fire on an enemy’s buildings or his ships, and so destroy them. Burning torches were thrown by machines, made of cords and springs, over a city wall, and it became a great study to find the best burning compound with which to cover these torches. One was needed which would blaze with a great flame and was hard to put out. Hence the early chemists made all possible mixtures of pitch, resin, naphtha, sulphur, saltpeter, etc.; “Greek fire” was one of the most famous. What Two Monks Discovered.