As tribes became more advanced, they used two pieces of flint with which to strike fire, and after the discovery of iron, the flint and iron were used. How many centuries these simple devices were essential to the progress and even to the life of tribes, is not known; but when we realize that but a few short years ago our fathers lighted the fire with flint and steel, and that before the percussion cap was invented, the powder in the musket was ignited by flint and hammer, we see how important to civilization were these simple devices of producing fire artificially. So simple an invention as the discovery of the friction match saved hours of labor and permitted hours of leisure to be used in other ways. It is one of the vagaries of human progress that a simple device remains in use for thousands of years before its clumsy method gives way to a new invention only one step in advance of the old. _Cooking Added to the Economy of the Food Supply_.--Primitive man doubtless consumed his food raw. The transition of the custom of uncooked food to cooked food must have been gradual. We only know that many of the backward tribes of {91} to-day are using primitive methods of cooking, and the man of the Stone Ages had methods of cooking the meat of animals. In all probability, the suggestion came as people were grouped around the fire for artificial heat, and then, either by intention or desire, the experiment of cooking began. After man had learned to make water-tight baskets, a common device of cooking was to put water in the basket and, after heating stones on a fire, put them in the basket to heat the water and then place the food in the basket to be cooked. This method is carried on by the Indians in some parts of Alaska to this day, where they use a water-tight basket for this purpose. Probably this method of cooking food was a later development than the roasting of food on coals or in the ashes, or in the use of the wooden spit. Catlin, in his _North American Indians_, relates that certain tribes of Indians dig a hole in the ground and line it with hide filled with water, then place hot stones in the water, in which they place their fish, game, or meat for cooking. This is interesting, because it carries out a more or less universal idea of adaptation to environment. Probably the plains Indians had no baskets or other vessels to use for this purpose, but they are found to have used similar methods of cooking grasshoppers. They dig a hole in the ground, build a fire in the hole, and take the fire out and put in the grasshoppers. Thus, they have an exhibition of the first fireless cooker.