442 TROPICAL NATURE VIUT 
are made of a curidus 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 Reports 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 Paleolithic 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, 
