It is held that the nascent civilization of these Egyptians of the Neolithic, or late Stone Age, was overthrown by the invading hosts of a more highly civilized race which probably came from the East, and which may have been of a Semitic stock. The presumption is that this invading people brought with it a knowledge of the arts of war and peace, developed or adopted in its old home. The introduction of these arts served to bridge somewhat suddenly, so far as Egypt is concerned, that gap between the prehistoric and the historic stage of culture to which we have all along referred. The essential structure of that bridge, let it now be clearly understood, consisted of a single element. That element is the capacity to make written records: a knowledge of the art of writing. Clearly understood, it is this element of knowledge that forms the line bounding the historical period. Numberless mementos are in existence that tell of the intellectual activities of prehistoric man; such mementos as flint implements, pieces of pottery, and fragments of bone, inscribed with pictures that may fairly be spoken of as works of art; but so long as no written word accompanies these records, so long as no name of king or scribe comes down to us, we feel that these records belong to the domain of archaeology rather than to that of history. Yet it must be understood all along that these two domains shade one into the other and, it has already been urged, that the distinction between them is one that pertains rather to modern scholarship than to the development of civilization itself. Bearing this distinction still in mind, and recalling that the historical period, which is to be the field of our observation throughout the rest of our studies, extends for Egypt well back into the fifth millennium B.C., let us briefly review the practical phases of that civilization to which the Egyptian had attained before the beginning of the dynastic period. Since theoretical science is everywhere linked with the mechanical arts, this survey will give us a clear comprehension of the field that lies open for the progress of science in the long stages of historical time upon which we are just entering.