nt,
and, if I am not mistaken, the great railway bridge right across the very
mouth of the river has, in the last few months, been made the boundary of
the reclaimed land.

Now, Blanchetaque was an artificial ford. We know this because there is no
marl formation near by, and could be none forming a narrow rib across the
deep alluvial mud of the estuary; the marl, then, can only have been
brought from some little distance. It is not only an artificial hardening
which we have to deal with, but one in the midst of a tidal estuary where
a violent current swept the work for centuries. Finally, the cause for
keeping the ford in some sort of repair early disappeared in modern times
before the process of reclaiming the land of the estuary began. Numerous
modern bridges, coupled with the great development of modern roads,
permitted the crossing of the Somme at and below Abbeville: notably the
Bridge of Cambron. The railway, the growth of the tonnage of steamers, and
other causes, led to the decline of the little riverside town of
Port--formerly the secure head of marine navigation upon the river and
largely the cause that Blanchetaque was kept in repair.

Again, the reclamation of the land has been carried out with a French
thoroughness only too successful in destroying the contours of the old
river bed. In the sketch map on p. 60 I have indicated to the best of my
ability the channel of the river at low tide as it appears to have been
before reclamation began, but even this can barely be traced upon the
levelled, heightened, and now fruitful pastures.

It is all this which has made the exact emplacement of Blanchetaque so
difficult to ascertain, and has led to the controversies upon its site.

Now, if we will proceed to gather all forms of evidence, we shall find
that they converge upon one particular line of trajectory which in the end
we can regard as completely established.

We have in the first place (and most valuable of all, of course)
tradition. Local traditions luckily carefully gathered as late as
1840,[10] but the indications of the peasants pointing out the traditional
site of the then ruined way were, unfortunately, not marked on a map. What
_was_ done was to give an indication unfortunately not too precise, and to
leave it on record that the northern end of the ford was "from 1200 to
1500 metres below Port." This gives us a margin of possible error, not of
300 yards as might be supposed, but of more than double