proportion of collegiate institutions, not only
monastic but military; the life in common which spread as a habit to
so many parts of society beyond the monastic; the large families which
(from genealogy) we can trust to be as much a character of the early
Middle Ages as they, were not the character of the later Middle Ages,
the crowd of semi-servile dependants which would be discovered in any
large house--all these make us perfectly safe in multiplying by at
least ten the number of households counted in the Survey if we would
get at the population of those households, and it must be remembered
that the houses counted, even in those parts of England which were
fairly thoroughly surveyed, can only represent a _minimum_ number,
whatever was the method of counting. The lists may in some instances
include every single household in a place, though from what we know of
the diversity of local custom this is unlikely. In most places it is
far more likely that the list covered but some portion that by custom
owed a public tax, and this is especially true of the towns.

After Dorchester, which was the first of the fortresses of the Thames,
so far as we have any knowledge, and after Oxford, which came next,
and appears to have been founded since the beginning of recorded
history in these islands, there remain to be considered the other
strongholds which held the line of the valley.

It would be easy to multiply these if one were to consider all
fortifications whatsoever connected with the general strategic line
formed by the Thames, but such a catalogue would exceed the boundaries
set to this book. It is proposed to consider only those which were
strictly connected with the passage of the stream, and of such there
are but three besides Dorchester and Oxford, for that at Cricklade is
doubtful, and in any case determines a passage which could be always
outflanked upon either side, while the great fortress of the Tower,
lying as it does upon the estuarial Thames below bridges, does
directly protect a highway.

These three strongholds directly connected with the inland river are
Wallingford, Reading and Windsor, and of the three Wallingford and
Windsor were more directly military: the last, Reading, appears to
have been but an adjunct to a large and civil population; the fourfold
quality of Reading in the history of the Thames, as a civil
settlement, as a religious centre, as a stronghold, and as one of the
very few examples of mod