It is the custom among archæologists to divide early culture into periods, according to the weapons in use. Accordingly we say that the Ægean periods extend from the Neolithic to the Late Bronze Age, meaning that the earliest of these Ægean potsherds are found in conjunction with polished flint weapons and tools, while along with the latest we find a few rare pieces of iron, but mostly bronze of a very high finish and workmanship. Such finds are dated very roughly by the level at which they lie, because it is a curious but certain fact that the level of ground once built over is constantly rising through accretions of dust and débris. Anyhow, it will be clear to every one that when, as at Troy and Cnossos, we find a series of buildings each superimposed upon the ruins of another, we can trace the history of such a site from early to late with certainty. Sometimes it is possible also to get a date by examining foreign objects found on the same site, such as gems bearing the cartouche or sign-royal of Egyptian kings. Only we must bear in mind that such little objects are easily displaced and often preserved for many centuries, so that great care must be used in taking them as evidence. Also, serious conflicts are still going on between the Egyptologists, and their dates are by no means ascertained facts at present. PROGRESS OF ÆGEAN CULTURE I have said that the prehistoric culture revealed by the excavations in Crete and elsewhere forms a continuous and progressive history from the Stone Age to the Iron Age. Sir Arthur Evans, indeed, has divided his discoveries into nine periods, from “Early Minoan I.” to “Late Minoan III.” Without being quite so precise, let us attempt to sketch a history of “prehistoric” civilisation on Greek soil, taking Crete as the centre of influence. [Illustration: Black Vase from Cyprus] “Neolithic man” in Crete, though his weapons and tools were but polished stones, and far as he was behind his Neolithic brothers of Central Europe, had already begun to design patterns upon his pottery. Like Nature abhorring a vacuum, he traced zigzags, triangles, and chevrons upon the plastic clay, scratching or pricking lines and dots with a point of bone or stone, and sometimes filling the holes and scratches with white gypsum to show up the pattern. The body of his vases was generally black and shiny. Bucchero nero, as the Italian archæologists call it, is found in the Neolithic strata all over Southern Europe. [Illustration: Plan of Neolithic House]