Thus I conceive the intention and management of this famous work, the Roman wall. It reaches 90 Roman miles: this is distributed into nine parts by one of the largest castles, or cities: that interval has six lesser castles. The names of the larger, till I am better informed, are thus: 1. _Blatum Bulgium_, Boulness; 2. _Drumabon_, Drumburg castle; 3. _Luguvallum_, Carlisle; 4. _Amboglauna_, Castlesteeds; 5. _Voreda_, Caer Voran; 6. _Borcovicus_, Housesteeds; 7. _Procolitia_, Caerhaw brough; 8. _Hunnum_, Portgate; 9. _Vindolana_, Ruchester; 10. _Banna_, Newcastle. The great castles were generally 400 foot square: these held a cohort; the lesser held a maniple, or century: the first consisted of 600, the other of 120 men; for the Romans, in their military affairs especially, reckoned by dozens. Thus the great castles contained a full legion, 6000 men; the lesser, or centuries, a legion and half: the cohorts were the standing garrison; the centuries were the watch: for the Romans did not, as at present, set a single man to watch over an army; but they watched by centuries, whence we have got the word of standing _century_, without the thing. This I suppose the primary disposition, whence it was provided that two legions and a half should be a sufficient force to render this wall impregnable; and no doubt it was so, as long as the Romans continued here. Further, upon the mouths of the rivers were the fleets and galleys, to prevent the enemy from passing them in their boats, as the _Cohors Ælia classica_ at _Tunnocelum_, or Tynmouth, as the _Notitia Imperii_ in the last times informs us. As also, of the disposition of the other troops along the Wall, and castles adjacent at that time. Notwithstanding the foregoing method of planting these castles, as the regular and primary intention of the Romans, in such regular distances that they may relieve one another as occasion requires; yet it must be understood with allowance, and accordingly we find it so: they were not so strict as to plant their castles at the alligned distances indiscriminately, for that would be ridiculous; but chose out all along the nearest ground to those distances, which by situation, on hills and the like, best suited the end, for strength, prospect, water, and all other conveniencies: they likewise placed them thinner, or more frequent, as the more or less defensible parts of the Wall required. [Sidenote: TAB. LXXVII.]