One day Professor Flinders Petrie came across remains. The greatest care was exercised in digging, so that every shred of evidence could be collected, and as the sand and soil were drawn aside he saw it was a very ancient grave, older than anything ever dreamed of in connection with Egypt. No one had any idea that Egypt was inhabited so long ago, but here was proof that men lived in the Nile valley in the dark ages of Time. The evidence goes to show that a crude civilization existed there ten thousand years ago, and that men may have lived in the Nile valley over twenty thousand years ago. Whether any relics will ever be found to throw any light on this epoch of Egyptian history remains to be seen, but it would not be astonishing if something did eventually appear, for the country has powers of preservation which even to-day are only faintly recognized, and the earth can hide things so cunningly that human beings may search for centuries and never find them again. The fact that they are not found is no proof that they never existed. When this ancient man hunted on the banks of the Nile, he gazed upon a very different land from that which exists to-day. The river was wider and shallower. It overflowed its banks for greater distances. The banks of gravel which show where the waters of the river lapped in bygone centuries still exist, but they are far removed from the river, and a hundred feet or so higher. In all the thousands of years that have elapsed since then, the Nile has been cutting a deeper and deeper channel for itself. In all the years that it has been bringing down the mud in solution, flowing over the land, some of the mud has sunk to the bottom and remained; much of it has been carried from the Delta to the sea. The mud that sank has got deeper and deeper. The river has added to the deposit inch by inch, until there is now a wonderful layer of alluvial soil: just the mud of the Nile, between 30 and 40 feet thick on each side of the stream. This deposit itself has helped to give scientists an idea of the age of the earliest human remains that have been found. The rate at which the river leaves the mud behind has been carefully measured, and men have learned that in a century the Nile will add 4 inches of soil to the fields by flooding. Test holes have revealed the present depth of the alluvial, and if roughly about a yard of deposition is allowed for one thousand years, and about 10 or 12 yards are allowed for the depth, then the age of the deposit is fixed at ten or twelve thousand years.