Planned archeological digging is only about a century old. Even before this, however, a few men realized the significance of objects they dug from the ground; one of these early archeologists was our own Thomas Jefferson. The first real mound-digger was a German grocer’s clerk, Heinrich Schliemann. Schliemann made a fortune as a merchant, first in Europe and then in the California gold-rush of 1849. He became an American citizen. Then he retired and had both money and time to test an old idea of his. He believed that the heroes of ancient Troy and Mycenae were once real Trojans and Greeks. He proved it by going to Turkey and Greece and digging up the remains of both cities. Schliemann had the great good fortune to find rich and spectacular treasures, and he also had the common sense to keep notes and make descriptions of what he found. He proved beyond doubt that many ancient city mounds can be _stratified_. This means that there may be the remains of many towns in a mound, one above another, like layers in a cake. You might like to have an idea of how mounds come to be in layers. The original settlers may have chosen the spot because it had a good spring and there were good fertile lands nearby, or perhaps because it was close to some road or river or harbor. These settlers probably built their town of stone and mud-brick. Finally, something would have happened to the town--a flood, or a burning, or a raid by enemies--and the walls of the houses would have fallen in or would have melted down as mud in the rain. Nothing would have remained but the mud and debris of a low mound of _one_ layer. The second settlers would have wanted the spot for the same reasons the first settlers did--good water, land, and roads. Also, the second settlers would have found a nice low mound to build their houses on, a protection from floods. But again, something would finally have happened to the second town, and the walls of _its_ houses would have come tumbling down. This makes the _second_ layer. And so on.... In Syria I once had the good fortune to dig on a large mound that had no less than fifteen layers. Also, most of the layers were thick, and there were signs of rebuilding and repairs within each layer. The mound was more than a hundred feet high. In each layer, the building material used had been a soft, unbaked mud-brick, and most of the debris consisted of fallen or rain-melted mud from these mud-bricks.