Yet there must have been at some point in the remote past an exception to this rule. Somewhere and somehow the people of Egypt must have developed from crude beginnings the architectural knowledge and resource which meet us in the oldest monuments, though every vestige of that early age has apparently perished. But although nothing has come down to us of the actual work of the builders who wrought in the primitive ages of mankind, there exist throughout Europe and Asia almost countless monuments of a primitive character belonging to relatively recent times, but executed before the advent of historic civilization to the regions where they are found. A general resemblance among them suggests a common heritage of traditions from the hoariest antiquity, and throws light on the probable character of the transition from barbaric to civilized architecture. +PREHISTORIC MONUMENTS.+ These monuments vary widely as well as in excellence; some of them belong to Roman or even Christian times; others to a much remoter period. They are divided into two principal classes, the megalithic structures and lake dwellings. The latter class may be dismissed with the briefest mention. It comprises a considerable number of very primitive houses or huts built on wooden piles in the lakes of Switzerland and several other countries in both hemispheres, and forming in some cases villages of no mean size. Such villages, built over the water for protection from attack, are mentioned by the writers of antiquity and portrayed on Assyrian reliefs. The objects found in them reveal an incipient but almost stationary civilization, extending back from three thousand to five thousand years or more, and lasting through the ages of stone and bronze down into historic times.