VIII THE ANTIQUITY OF MAN IN NORTH AMERICA 447 
of clay and gravel. The most remarkable discovery, however, 
is that known as the Calaveras skull. In the year 1866 some 
miners found in the cement, in close proximity to a petrified 
oak, a curious rounded mass of earthy and stony material 
containing bones, which they put on one side, thinking it was 
a curiosity of some kind. Professor Wyman, to whom it was 
given, had great difficulty in removing the cemented gravel 
and discovering that it was really a human skull nearly entire. 
Its base was embedded in a conglomerate mass of ferruginous 
earth, water-worn volcanic pebbles, calcareous tufa, and frag- 
ments of bones, and several bones of the human foot and 
other parts of the skeleton were found wedged into the 
internal cavity of the skull. Chemical examination showed 
the bones to be in a fossilised condition, the organic matter 
and phosphate of lime being replaced by carbonate. It was 
found beneath four beds of lava, and in the fourth bed of 
gravel from the surface ; and Professor Whitney, who after- 
wards secured the specimen for the State Geological Museum, 
has no doubt whatever of its having been found as described. 
In Professor Whitney’s elaborate Report on the Auriferous 
Gravels of the Sierra Nevada, from which most of the pre- 
ceding sketch is taken, he arrives at the conclusion that 
the whole evidence distinctly proves “that man existed in 
California previous to the cessation of volcanic activity in the 
Sierra Nevada, to the epoch of greatest extension of the 
glaciers in that region, and to the erosion of the present river- 
canons and valleys, at a time when the animal and vegetable 
creations differed entirely from what they are now, and 
when the topographical features of the State were extremely 
unlike those exhibited by the present surface.” He elsewhere 
states that the animal and vegetable remains of these deposits 
prove them to be of “at least as ancient a date as the 
European Pliocene.” 
Professor Whitney enumerates two other cases in which 
human bones have been discovered in the auriferous gravel, 
and in one of them the bones were found by an educated 
observer, Hr. Boyce, M.D., under a bed of basaltic lava eight 
feet thick ; but these are of but little importance when com- 
pared with the preceding cases, as to which we have such full 
and precise details. The reason why these remarkable dis- 
