(4.) Attempts have been made to estimate the antiquity of man from the animal races with which his remains have been found associated. The animals brought into this estimate have been chiefly the mammals, quadrupeds, most nearly related, by anatomical structure, to man. Great account has been made of the fact that the remains of man (his bones or his tools) have been found in connection with the remains of land animals now extinct. The uncertain element in all such calculations is the date at which the said animal species became extinct. This is perhaps fully as doubtful as the age at which man began to live on the earth. So far as is known, some species have disappeared within the present century; _e. g._ the Great Auk, or Northern Penguin (alca impennis), last seen alive in 1844. Several species, once quite prominent for their hugeness or other qualities, are supposed to have disappeared within the historic period of man; _e. g._ the mammoth, the mastodon, the woolly rhinoceros, the cave-bear, etc. But precisely _when_ they severally became extinct, no existing data suffice to show. Of course it avails little to prove that man was coeval with a few animal races now extinct. (5.) Far more important in my view is the light thrown upon the antiquity of the Bronze and Iron ages of civilization in Northern and Western Europe by the traces of commercial relations between those respective peoples and the civilized nations of the known historic ages. In this case, the elements of uncertainty common to the preceding estimates are mostly if not wholly eliminated. When among the relics of the Bronze age, say in Switzerland or in Denmark, we find art-specimens, valuable for use or beauty, which manifestly came from Phenicia, Etruria, or Egypt, bearing unmistakably the stamp of their civilization, and specifically, of their art, we need no further proof that the old Bronze age lay _in time_ along-side of the reign of Etrurian or Egyptian art and civilization. On this subject the British Quarterly (Oct., 1872) on “The present Phase of Pre-historic Archeology” discusses the question whether the Bronze civilization in Central and Northern Europe was introduced by an invading people from the East, or by peaceful commerce with the peoples contiguous to the Mediterranean, viz. the Phenicians of Palestine, the Etrurians of Italy, and the Egyptians. The argument is strongly in favor of the latter alternative. “The beautiful bronze swords, spear-heads, axes, knives, razors, etc., which lie scattered over Northern and Central Europe are remarkable for the singular beauty of their form and ornamentation”――all bearing so much unity of design as to prove a common origin from the same source. “The double spirals, and dotted circles and spirals and zigzag ornaments which are so common on the bronze articles of France, Germany, Britain, Ireland, and Scandinavia _are identical with the designs which are found in Etruscan tombs_. Some of the bronze swords and spear-heads