13 
number of these cases stone implements, of undoubted human 
origin, have been found under several successive sheets of basalts, 
tufts, and gravels, and in a few, as in the celebrated skull of 
Calaveras, human bones have been found under circumstances 
which it seems the height of unreasoning scepticism to dispute. 
Any doubt which might have existed as to the great antiquity of 
these gravels, and the human origin of the implements found in 
them, has been removed by a paper read recently before the 
Anthropological Society of London by Mr. Skertchley, the well- 
known geologist, to whom we are indebted for the discovery of 
paleolithic implements below the chalky boulder-clay at Brandon, 
in Suffolk. He visited California and brought back specimens of 
rude stone mortars of undoubted human origin, which were found 
in great numbers in a deposit of white sands and gravels, 450 feet 
thick, below a basalt cap varying from 25 to 100 feet in thickness. 
He says of those sands, “ If the human remains had not been 
found in these geologists would never have doubted their tertiary 
age. Atany rate they must be of immense antiquity. Since 
they were deposited the present river system of the Sacramento, 
Joaquim, and other large rivers has been established ; canons 
2,000 feet deep have been excavated by those later rivers through 
lava, gravels, and into the bed rock ; and the gravels, once the 
bed of a large river, now cap hills 6,000 feet high.” 
Vast AccuMULATIONS OF Mup. 
The deposit of loess which fills up so many of the valley systems 
of Europe, Asia, and America to such great depths, and spreads 
over the adjacent table-lands, has always seemed to me a most 
conclusive proof of the great antiquity of the glacial period. It 
is a tranquil land deposit of fine glacial mud, from sheets of water 
which have inundated the country when the great rivers from 
glaciated districts ran at higher levels and gradually excavated 
their present valleys. Lyell estimates that the thickness of this 
deposit in the Rhine valley must have been at least 800 feet, 
admitting that the thin beds of léess found at much higher levels 
may be due to melting snow rather than to rivers. It is not 
marine, or lacustrian, but distinctly such a deposit as that of the 
Nile mud accumulated by annual inundations in the delta of 
Egypt. It is difficult to see how such an accumulation of fine 
glacial mud can have gone on faster than that of the Nile mud, 
which is estimated at about three inches per century. But at this 
rate 800 feet of léess would have required 320,000 years to accumu- 
late, and a great deal of it is certainly posterior to the second or 
‘latter period of maximum glaciations. The difficulty here again 
is to see, not how the geological facts require the time assigned by 
Croll’s theory for the phases of the glacial period, but how they 
can be compressed within such narrow limits. In any case it is 
certain that human remains, associated with a fauna of the early 
