In passing from the historical period, in which we can appeal to written records and monuments, into that of palæontology and geology, where we have to rely on scientific facts and reasons, we have to traverse an intermediate stage in which legends and traditions still cast a dim and glimmering twilight. The first point to notice is that this, like the twilight of tropical evenings, is extremely brief, and fades almost at once into the darkness of night. It is singular in how short a time all memory is lost of events which are not recorded in some form of writing or inscription, and depend solely on oral tradition. Thus it may be safely affirmed that no nation which has passed into the metal age retains any distinct recollection of that of polished stone, and _à fortiori_ none of the palæolithic period, or of the origins of their own race or of mankind. The proof of this is found in the fact that the stone axes and arrow-heads which are found so abundantly in many countries are everywhere taken for thunderbolts or fairy arrows shot down from the skies. This belief was well-nigh universal throughout the world; we find it in all the classical nations, in modern Europe, in China, Japan, and India. Its antiquity is attested by the fact that neolithic arrow-heads have been found attached as amulets in necklaces from Egyptian and Etruscan tombs, and palæolithic celts in the foundations of Chaldæan temples. In India many of the best specimens of palæolithic implements were obtained from the gardens of ryots, where they had been placed on posts, and offerings of ghee duly made to them. Like so many old superstitions, this still lingers in popular belief, and the common name for the finely-chipped arrow-heads which are so plentifully scattered over the soil from Scotland to Japan, is that of elf-bolts, supposed to have been shot down from the skies by fairies or spirits. Until the discoveries of Boucher-de-Perthes were confirmed only half a century ago, this belief was not only that of simple peasants, but of the learned men of all countries, and the volumes are innumerable that have been written to explain how the "cerauni," or stone-celts, taken to be thunderbolts, were formed in the air during storms. They are already described by Pliny, and a Chinese Encyclopædia says that "some of these lightning stones have the shape of a hatchet, others of a knife, some are made like mallets. They are metals, stones, and pebbles, which the fire of the thunder has metamorphosed by splitting them suddenly and uniting inseparably different substances. On some of them a kind of vitrification is distinctly to be observed."