Second, to issue copper, this device was again adopted, and still abides with us.  The very large number of types (approaching a hundred) of the Romano-British coinage, from this reign to that of Caracalla, shows that Hadrian inaugurated the system of minting coins not only with reference to Britain, but for special local use.  They were doubtless struck within the island; but we can only conjecture where the earliest mints were situated.

D. 5.—­Twenty years after Hadrian’s visit we again find (A.D. 139) some little trouble in the north, owing to a feud between the Brigantes and Genuini, a clan of whom nothing is known but the name.  The former seem to have been the aggressors, and were punished by the confiscation of a section of their territory by Lollius Urbicus, the Legate of Antoninus Pius; who further “shut off the excluded barbarians by a turf wall” (muro cespitio submotis[266] barbaris ducto).  The context connects this operation with the Brigantian troubles; but it is certain that Lollius repaired and strengthened Agricola’s rampart between Forth and Clyde.  His name is found in inscriptions along that line,[267] and that of Antoninus is frequent.  This work consisted of a vallum some 40 miles in length, from Carriden to Dumbarton, with fortified posts at frequent intervals.  It is locally known as “Graham’s Dyke,” and, since 1890, has been systematically explored by the Glasgow Archaeological Society.  It is in the strictest sense “a turf wall”—­no mere grass-grown earthwork, but regularly built of squared sods in place of stones (sometimes on a stone base).  Roman engineers looked upon such a rampart as being the hardest of all to construct.

SECTION E.

Commodus Britannicus—­Ulpius Marcellus—­Murder of Perennis—­Era of military turbulence—­Pertinax—­Albinus—­British Army defeated at Lyons—­Severus—­Caledonian war—­Severus overruns Highlands.

E. 1.—­It may very probably be owing to the energy of Lollius that Britain, “Upper” and “Lower” together as it seems, as inscriptions tell us, was about this date ranked amongst the Senatorial Provinces of the Empire, the Pro-consul being C. Valerius Pansa.  That it should have been made a Pro-consulate shows (as is pointed out on p. 142) that they were now considered amongst the more peaceful governorships.  In fact, though some slight disturbances threatened at the death of Antoninus (A.D. 161), the country remained quiet till Commodus came to the throne (A.D. 180).  Then, however, we hear of a serious inroad of the northern barbarians, who burst over the Roman Wall and were not repulsed without a hard campaign.  The Roman commander was Ulpius Marcellus, a harsh but devoted officer, who fared like a common soldier, and insisted on the strictest vigilance, being himself “the most sleepless of generals."[268] The British Army, accordingly, swore by him, and were minded to proclaim him Emperor,[2] a matter which all but cost