And, furthermore, it is doubtful if we can ever go very far in solving the problem of man in the Andes. Although they made great progress in architecture, agriculture, engineering, and the science of government, the ancient Peruvians did not achieve the art of writing, nor did they even reach the stage of hieroglyphics. Their records were kept on _quipus_ (kee-poos), variously colored strings with many different kinds of knots. These seem, however, to have been used only for accounting purposes. Thus far, the _quipus_ in possession of our archeologists have been of no particular aid in deciphering the history of their makers. Accordingly, what we know of the Incas consists of traditions gathered together by early Spaniards, and the work of present-day students who, by modern archeological methods, are slowly bringing some light to bear on this apparently insolvable problem. [Illustration: PISAC Terraces below the principal ruins, still used for growing wheat and barley] [Illustration: DOORWAY In ruins, now known as Rosaspata, but which Dr. Bingham has shown are probably those known to the Incas as “Vitcos,” the last home of the Incas] _Origin of American Aborigines_ Although there are many ideas advanced as to the origin of the American aborigine, it is commonly believed that he came from northeastern Asia and gradually moved southward. Archeologists and geologists are all agreed that he arrived at the close of the glacial epoch, long after the disappearance of the prehistoric animals which Dr. Matthew described for Mentor readers some time ago. When he came to this continent he had probably already reached the higher stages of the Stone Age, and was possibly already in the Bronze Age. Just how long it has been since his arrival we cannot tell.