E. 5.--Severus, in spite of age and infirmity,[276] responded to the call, and, in a marvellously short time, appeared in Britain, bringing with him his worthless sons, Caracalla[277] and Geta[278]--"my Antonines," as he fondly called them,[279] though his life was already embittered by their wickedness,--and Geta's yet more worthless mother, Julia Domna. Leaving her and her son in charge south of Hadrian's Wall, Severus and Caracalla undertook a punitive expedition[280] beyond it, characterized by ferocity so exceptional[281] that the names both of Caledonians and Meatae henceforward disappear from history. The Romans on this occasion penetrated further than even Agricola had gone, and reached Cape Wrath, where Severus made careful astronomical observations.[282] E. 6.--But the cost was fearful. Fifty thousand Roman soldiers perished through the rigour of the climate and the wiles of the desperate barbarians; and Severus felt the north so untenable that he devoted all his energies to strengthening Hadrian's Wall,[283] so as to render it an impregnable barrier beyond which the savages might be allowed to range as they pleased.[284] E. 7.--In what, exactly, his additions consisted we do not know, but they were so extensive that his name is no less indissolubly connected with the Wall than that of Hadrian. The inscriptions of the latter found in the "Mile Castles" show that the line was his work, and that he did not merely, as some have thought, build the series of "stations" to support the "Vallum." But it is highly probable that Severus so strengthened the Wall both in height and thickness as to make it[285] far more formidable than Hadrian had left it. For now it was intended to be the actual _limes_ of the Empire. SECTION F. Severus completes Hadrian's Wall--Mile Castles--Stations--Garrison--Vallum--Rival theories--Evidence--Remains--Coins--Altars--Mithraism--Inscription to Julia Domna--"Written Rock" on Gelt--Cilurnum aqueduct.