The roundheads comprise the Alpine subspecies. This is the strongest numerical group to-day. It is characterized by small round heads, short bodies, dark hair, and dark eyes. It is of Asiatic origin and includes the Slavs, modern Greeks, Italians, Germans, Austrians, Swiss, the pre-Nordic Irish, French, and Belgians. The first Alpine invasion of Europe began about 10,000 B. C. There were many subsequent ones through the plateaus of Asia Minor, the Balkans, and valley of the Danube. They reached England about 1800 B. C., and formed small colonies in Ireland, the descendants of which now call themselves Celts and are clearly distinguished by the characteristic Alpine indices. This race is now so well acclimatized in Europe that most of its Asiatic traces have been lost, and its round skulls and dark eyes and hair are the only reminders of its Mongolian origin. Members of each of these three great racial groups of mankind have throughout the ages contributed to the development of the sciences and arts. The Nordics began to appear in European history as agricultural tribes, speaking Aryan languages, like Celtic and Welsh, who swept down from the north and pushed the earlier settlers back through their irresistible arms, which were made of bronze and later of iron. The earlier settlers were still furnished with arms and implements of the Stone Age. There was a much older intellectual people than the Nordics settled in Europe. The people of this race, about whom we have learned through recent archæological researches, are known as the Cro-Magnons. They lived between 25,000 and 10,000 B. C. Their skulls were distinguished from those of the Nordics by their pronounced cheek-bones and broad faces. Their culture, as their favorable cephalic index would suggest, was of a high character. Numerous drawings and art works of theirs, which have been preserved, place them among the world's superior peoples. Soon after the settlement of the Cro-Magnons in Europe, and their intermarriage with the earlier settlers, their physical development and stature began to decline. They were finally absorbed and destroyed by the inferior peoples among whom they dwelled. Their disappearance, like that of the ancient Greeks, who appear to have been the most intellectual people the world ever produced, shows how the upward development of human physical and intellectual qualities is constantly injured by the contacts of superior and inferior races. The scientific discoveries made prior to the Iron Age, or about 2000 B. C., were not numerous. The struggle for life was so intense that few had opportunity for contemplation and philosophic reflection. It was subsequent to the discovery of the basic principles of metallurgy, in the Iron Age, that science began rapidly to advance. The benefits bestowed upon mankind by the employment of metals reduced the sharpness of life's struggles, permitted and instigated reflection, and provided means for experimentation.