dispatch of carefully selected parties of emigrants, and the
French activity in missionary work and in exploration became
bolder than ever. Pere Marquette and the Sieur de la Salle traced
out the courses of the Ohio and the Mississippi; French trading-
stations began to arise among the scattered Indian tribes who
alone occupied the vast central plain; and a strong French claim
was established to the possession of this vital area, which was
not only the most valuable part of the American continent, but
would have shut off the English coastal settlements from any
possibility of westward expansion. These remarkable explorations
led, in 1717, to the foundation of New Orleans at the mouth of the
great river, and the organisation of the colony of Louisiana. But
the whole of the intense and systematic imperial activity of the
French during this period depended upon the support and direction
of government; and when Colbert died in 1683, and soon afterwards
all the resources of France were strained by the pressure of two
great European wars, the rapid development which Colbert's zeal
had brought about was checked for a generation. Centralised
administration may produce remarkable immediate results, but it
does not encourage natural and steady growth. Meanwhile the
English had awakened to the fact that England had, almost by a
series of accidents, become the centre of an empire, and to the
necessity of giving to this empire some sort of systematic
organisation. It was the statesmen of the Commonwealth who first
began to grope after an imperial system. The aspect of the
situation which most impressed them was that the enterprising
Dutch were reaping most of the trading profits which arose from
the creation of the English colonies: it was said that ten Dutch
ships called at Barbados for every English ship. To deal with this
they passed the Navigation Act of 1651, which provided that the