contact with a civilised people, were ignorant of the strength of a
disciplined army, came down from their fortresses in the mountains
into the lower ground. A battle was fought near the Graupian Hill,
which seems to have been situated at the junction of the Isla and the
Tay. Agricola gained a complete victory, but he was unable to follow
the fugitives into their narrow glens, and he contented himself with
sending his fleet to circumnavigate the northern shores of the island,
so as to mark out the limits of the land which he still hoped to
conquer. Before the fleet returned, however, he was recalled by the
Emperor Domitian. It has often been said that Domitian was jealous of
his success; but it is possible that the Emperor really thought that
the advantage to be gained by the conquest of rugged mountains would
be more than counterbalanced by the losses which would certainly be
incurred in consequence of the enormous difficulty of the task.

[Illustration: Commemorative tablet of the Second Legion found at
Halton Chesters on the Roman Wall.]

24. =The Roman Walls.=--Agricola, in addition to his line of forts
between the Forth and the Clyde, had erected detached forts at the
mouth of the valleys which issue from the Highlands, in order to
hinder the Caledonians from plundering the lower country. In =119= the
Emperor Hadrian visited Britain. He was more disposed to defend the
Empire than to extend it, and though he did not abandon Agricola's
forts, he also built further south a continuous stone wall between the
Solway and the Tyne. This wall, which, together with an earthwork of
earlier date, formed a far stronger line of defence than the more
northern forts, was intended to serve as a second barrier to keep out
the wild Caledonians if they succeeded in breaking through the first.
At a later time a lieutenant of the Emperor, Antoninus Pius, who
afterwards became Emperor himself, connected Agricola's forts
between the Forth and Clyde by a continuous earthwork. In =208= the
Emperor Severus arrived in Britain, and after strengthening still
further the earthwork between the Forth and Clyde, he attempted to
carry out the plans of Agricola by conquering the land of the
Caledonians. Severus, however, failed as completely as Agricola had
failed before him, and he died soon after his return to Eboracum.

[Illustration: View of part of the Roman Wall.]

[Illustration: Ruins of a Turret on the Roman Wall.]

[Illustration: Part