288 GEOGRAPHY FROM AUGUSTUS TO TRAJAN. [CHAP.
between them by establishing a chain efforts across it1. He even
penetrated into Caledonia to the northward of this line, and
defeated the natives in two great battles. It was Agricola's good
fortune to have his exploits recorded by Tacitus, who was his son-
in-law, and through him we obtain an idea of the impression which
the natural features of Britain produced on the foreigners. Thus,
besides noticing the mildness and raininess of the climate, the
shortness of the summer nights, and other peculiarities, he specially
remarks on the depth to which the sea on these coasts penetrates
into the land, and on the numerous estuaries which are formed in
this manner8. Tacitus also records in his Agricola the expedition
which was despatched by that commander to explore the shores
of the island as far as its northern extremity, and he mentions
that they reached the Orcades (Orkneys). The land which they
saw in the distance beyond this point, but did not visit owing to
the lateness of the season, and which they believed to be Thule,
is no doubt the same to which Pytheas also assigned that name-
Mainland, the chief of the Shetland islands3. In Hadrian's time
(119 A.D.) the northern portion of these new conquests was
abandoned, and that emperor fixed the line of the Eden and the
Tyne as the limit of the Roman possessions, and constructed there
the famous rampart, which is known at the present day as the
Roman Wall. This continued to be the boundary until under
and Antoninus Antoninus Pius (142 A.D.) the country as far as the
Pius- Forth and the Clyde was again occupied, and a
continuous rampart of earth was built across the isthmus parallel
to the line of forts which Agricola had erected. By means of
these campaigns, and of the numerous settlements that were
founded in the country, and the roads by which they were con-
nected with one another, the Romans acquired a satisfactory
knowledge of the characteristics of Britain, and of the position
of the tribes by whom it was inhabited.
1 Tac. Agric., 23 ; Clota et Bodotria, diversi maris fluctibus per inmensum
revectae, angusto terrarum spado dirimuntur: quod turn praesidiis firmabatur.
3 Agric., 10; Unum addiderim, nusquatn laths dominari mare, multum
fluminum hue atque illuc ferre, nee litore tenus adcrescere aut resorberi, sed
influere penitus atque ambire, et iugis etiam ac montibus inseri velut in suo.
* MiiUeuhoff3 Deutsche Altertumskunde, x.p. 388.