Among our Anglo-Saxon ancestors the ordeal by fire was one of the modes of trying cases of law. The accused was compelled to walk blindfolded over red-hot plowshares. If these burned him, he was adjudged guilty; if not, he was acquitted, for it was supposed that the purity of fire would not permit an innocent man to suffer. The custom of the North American Indians was to discuss important tribal affairs around the council fire. Each sachem marched around it thrice, turning to it all sides of his person. Among peoples in both hemispheres it has been the practice to free fields from the demons of barrenness by lighting huge fires. The fields were supposed to be made fertile as far as the flames could be seen. In Bavaria seeds were passed through fire before they were sown to insure fertility. In some places children were held over the flame of an altar fire for purposes of purification. Nothing has played a more important part in the history of the race than fire. Human culture began with the use of it, and increased in proportion as its use increased. For ages man felt his helplessness before fire; he did not know how to produce it, or to turn it to good account. By and by the secret was discovered; mind began to gain the mastery over this great force. The most primitive method of producing fire artificially was by rubbing two sticks together. This method was probably discovered by accident. Fire from friction was caused also by pushing the end of a stick along a groove in another piece of wood, or by twirling rapidly a stick which had its end placed perpendicularly in a hole made in another piece of wood. Focusing the rays of the sun powerfully upon a given point by means of a lens or concave mirror, was another method used for starting fire. The story is told that when the ancient city of Syracuse in Sicily was being besieged, the great mathematician Archimedes, who was a resident of that city, set on fire the enemy's ships by focusing the sun's rays upon them with a mirror. In China the burning-glass was widely used not very long ago. When iron came into use, it was employed for making fire. A piece of flint was struck against an iron object. The concussion produced a spark, which fell into a box containing charred cotton called tinder. The tinder took fire but did not burst into flame. The flame came by touching the burning tinder with a strip of wood tipped with sulphur. This flint-and-steel method was used for producing fire until less than a century ago.