incomplete and indefinite. Within its own boundaries
the Roman government carefully collected every kind of information.
Such precision was indispensable for the carrying out of those Roman
principles of administration which will be described later. But of the
nations or tribes beyond the frontiers only so much was known as had
been gathered from a number of more or less futile campaigns, from
occasional embassies sent to Rome by such peoples, from the writings
of a few venturous travellers bent on exploration, from slaves who had
been acquired by war or purchase, or from traders such as those who
made their way to the Baltic in quest of amber, or to Arabia,
Ethiopia, and India in quest of precious metals, jewels, ivory,
perfumes, and fabrics.

There had indeed been sundry attempts to annex still more of the
world. Roman armies had crossed the Rhine and had twice fought their
way to the Elbe; but it became apparent to the shrewd Augustus and
Tiberius that the country could not be held, and the Rhine was for the
present accepted as the most natural and practical frontier. In the
East the attempts permanently to annex Armenia, or a portion of
Parthia, had so far proved but nominal or almost entirely vain.

On the Upper Euphrates at this date there was a sort of acknowledgment
of vague dependence on Rome, but the empire had acquired nothing more
solid. Forty years before our date a Roman expedition had penetrated
into South-west Arabia, of which the wealth was extravagantly
over-estimated, but it had met with complete failure. Into Ethiopia a
punitive campaign had been made against Queen Candace, and a loose
suzerainty was claimed over her kingdom, but the Roman frontier still
stopped short at Elephantine. Over the territories of the semi-Greek
semi-Scythian settlements to the north of the Black Sea Rome exercised
a protectorate, which was for obvious reasons not unwelcome to those
concerned. Along or near the eastern frontier she well understood the
policy of the "buffer state," and, within her own borders in those
parts, was ready to make tools of petty kings, whose own ambitions
would both assist her against external foes and relieve her of
administrative trouble.

At no time did the Roman Empire possess so natural or scientific a
frontier as at this, when it was bounded by the Rhine, the Danube, the
Black Sea, the Euphrates, the Desert, and the Atlantic. The only
exception, it will be perceived, was in Britain, but