442 TROPICAL NATURE 



are made of a curious granular argillite, the like of which I 

 do not know in the place," is an additional proof of it. The 

 further fact that the remains of man himself have been dis- 

 covered in the same deposit completes the demonstration. 

 First a human cranium was found of peculiar characteristics, 

 being small, long, and very thick ; then a tooth ; and, lastly, 

 a portion of a human under jaw, found at a depth of sixteen 

 feet from the surface, near where a fragment of mastodon 

 tusk had been found some years before. In recording this 

 last discovery the curator of the Peabody Museum remarks : 

 " To Dr. Abbott alone belongs the credit of having worked 

 out the problem of the antiquity of man on the Atlantic coast," 

 so that this gentleman appears to stand in a somewhat similar 

 relation to this great question in America as did Boucher de 

 Perthes in Europe. His researches are recorded in the first, 

 second, and third volumes of the Eeports of the Peabody 

 Museum. 



The interesting series of researches now briefly recorded 

 has led us on step by step through the several stages of the 

 quaternary at least as far back as the first great Glacial 

 period, thus corresponding to the various epochs of Neolithic 

 and Palaeolithic man in Europe, terminating in the Suffolk 

 flints, claimed to be pre- Glacial by Mr. Skertchley, or the 

 earliest traces of human occupancy in Kent's Cavern, of 

 which Mr. Pengelly states that " he is compelled to believe 

 that the earliest men of Kent's Hole were inter-Glacial if not 

 pre-Glacial." It now remains to adduce the evidence which 

 carries us much farther back, and demonstrates the existence 

 of man in Pliocene times. This evidence is derived from the 

 works of art and human crania found in the auriferous gravels 

 of California, and in order to appreciate duly its weight and 

 importance, it is necessary to understand something of the 

 physical characteristics of the country and the nature of the 

 gravels themselves, with their included fossils, since both 

 these factors combine to determine their geological age. 



The Auriferous Gravels of California 



The great lateral valleys of the Sierra Nevada are charac- 

 terised by enormous beds of gravel, sometimes in thick de- 

 posits on the sides or filling up the whole bed of the valley, 



