y must have looked before the present
deep valley was eroded.

In the case of the river Somme, we have a wide and deep valley, a large
part of which has been excavated in chalk rock, through which the river
now winds its way in a sinuous course to the English Channel. Yet we
feel sure that at some time in the past it was a mighty stream, and that
its waters surged along over a bed at least two hundred feet higher than
now. In proof of this fact we still find, at different places along
the chalky bluff, stretches of old gravel banks, laid down there by the
river, "reaching sometimes as high as two hundred feet above the present
water level, although their usual elevation does not exceed forty
feet."<32>

The history of the investigation of the ancient gravel beds of the Somme
is briefly this: More than one instance had been noted of the finding of
flint implements, apparently the work of men, in association with bones
of various animals, such as hyenas, mammoths, musk-sheep, and others,
which, as we have just seen, lived in Europe during the Glacial Age. In
a number of cases such finds had been made in caves. But for a long time
no one attributed any especial value to these discoveries, and various
were the explanations given to account for such commingling. A French
geologist, by the name of Boucher DePerthes, had noted the occurrence
of similar flint implements, and bones of these extinct animals, in a
gravel pit on the banks of the Somme, near Abbeville, France. He was
convinced that they proved the existence of man at the time these
ancient animals lived in Europe. But no one paid any attention to his
opinions on this subject, and a collection of these implements, which
he took to Paris in 1839, was scarcely noticed by the scientific world.
They were certainly very rude, and presented but indistinct traces of
chipping, and perhaps it is not strange that he failed to convince any
one of their importance. He therefore determined to make a thorough and
systematic exploration of these beds at Abbeville. In 1847 he published
his great work on this subject, giving over sixteen hundred cuts of the
various articles he had found, claiming that they were proof positive of
the presence of man when the gravels were depositing.

Picture of Flint Implements, so-called.------

Now there are several questions to be answered before the conclusions
of the French geologist can be accepted. In the first place, are these
so-calle