s hitherto fixed the extreme limits to which a
city could grow, and has exacted a compactness which has always been
very undesirable and which is now for the first time in the world's
history no longer imperative.

So far as we can judge without a close and uncongenial scrutiny of
statistics, that daily journey, that has governed and still to a very
considerable extent governs the growth of cities, has had, and probably
always will have, a maximum limit of two hours, one hour each way from
sleeping place to council chamber, counter, workroom, or office stool.
And taking this assumption as sound, we can state precisely the maximum
area of various types of town. A pedestrian agglomeration such as we
find in China, and such as most of the European towns probably were
before the nineteenth century, would be swept entirely by a radius of
four miles about the business quarter and industrial centre; and, under
these circumstances, where the area of the feeding regions has been very
large the massing of human beings has probably reached its extreme
limit.[16] Of course, in the case of a navigable river, for example, the
commercial centre might be elongated into a line and the circle of the
city modified into an ellipse with a long diameter considerably
exceeding eight miles, as, for example, in the case of Hankow.

If, now, horseflesh is brought into the problem, an outer radius of six
or eight miles from the centre will define a larger area in which the
carriage folk, the hackney users, the omnibus customers, and their
domestics and domestic camp followers may live and still be members of
the city. Towards that limit London was already probably moving at the
accession of Queen Victoria, and it was clearly the absolute limit of
urban growth--until locomotive mechanisms capable of more than eight
miles an hour could be constructed.

And then there came suddenly the railway and the steamship, the former
opening with extraordinary abruptness a series of vast through-routes
for trade, the latter enormously increasing the security and economy of
the traffic on the old water routes. For a time neither of these
inventions was applied to the needs of intra-urban transit at all. For a
time they were purely centripetal forces. They worked simply to increase
the general volume of trade, to increase, that is, the pressure of
population upon the urban centres. As a consequence the social history
of the middle and later thirds of the ninet