their ambition and turbulence had kept the government in
continual ferment, were reduced by the happiest art imaginable. Their
number, only two originally, was increased to four, by which their power
was balanced and broken. Their authority was not lessened, but its
nature was totally changed: for it became from that time a dignity and
office merely civil. The whole Empire was divided into four departments
under these four officers. The subordinate districts were governed by
their _vicarii_; and Britain, accordingly, was under a vicar, subject to
the _praefectus praetorio_ of Gaul. The military was divided nearly in the
same manner; and it was placed under officers also of a new creation,
the _magistri militiae_. Immediately under these were the _duces_, and
under those the _comites_, dukes and counts, titles unknown in the time
of the Republic or in the higher Empire; but afterwards they extended
beyond the Roman territory, and having been conferred by the Northern
nations upon their leaders, they subsist to this day, and contribute to
the dignity of the modern courts of Europe.

But Constantine made a much greater change with regard to religion by
the establishment of Christianity. At what time the Gospel was first
preached in this island I believe it impossible to ascertain, as it came
in gradually, and without, or rather contrary to, public authority. It
was most probably first introduced among the legionary soldiers; for we
find St. Alban, the first British martyr, to have been of that body. As
it was introduced privately, so its growth was for a long time
insensible; but it shot up at length with great vigor, and spread itself
widely, at first under the favor of Constantius and the protection of
Helena, and at length under the establishment of Constantine. From this
time it is to be considered as the ruling religion; though heathenism
subsisted long after, and at last expired imperceptibly, and with as
little noise as Christianity had been at first introduced.

[Sidenote: A.D. 368.]

In this state, with regard to the civil, military, and religious
establishment, Britain, remained without any change, and at intervals in
a tolerable state of repose, until the reign of Valentinian. Then it was
attacked all at once with incredible fury and success, and as it were in
concert, by a number of barbarous nations. The principal of these were
the Scots, a people of ancient settlement in Ireland, and who had thence
been tr