The second edition of Sir George Macdonald's Roman Wall in Scotland has provoked a new interest in the problems presented by that limes; and no contribution to the discussion is likely to be more stimulating than that propounded above (p. 80 ff.) by Professor Collingwood. The bold thesis there developed is that the Antonine Wall was the slightest of barriers, a toy frontier manned by a garrison whose energies were divided and wasted between patrolling and the legitimate work of defence. So curious a design resulted from the fact that the Lowlands between the Walls had been largely depopulated before the new frontier was established. This interesting view, coherent enough in itself, is put forward in order to supply a lack in Sir George's book, which studies the frontier objectively, without attempting to explain why it was erected; and it is freely admitted that the archaeological facts upon which such a view might be based are insufficient to justify an authoritative statement of a case. Thus, we are in the happy position of being able to admire both author and critics. Sir George's caution is ranged against Professor Collingwood's temerity ; the one avoiding treacherous ground, the other treading nimbly across it, getting a foothold where he can.