There is another remarkable piece of antiquity, the ancient building that went by the name of Arthur's O'on. Henry Sinclair, Dean of Glasgow about 1560, calls it 'Arthur's Huif'; and Gordon speaks of it as 'Arthur's Hoff'. Its site was a few yards to the north-east of the Forge Row, Carron, at the corner of an enclosure about 50 feet square, on the estate of Stenhouse. The destruction of this rare though rude relic of architecture by Sir Michael Bruce, in 1743, for the purpose of repairing a dam-head with the best of its stones, roused the wrath of all antiquarians. Maitland has inserted in his History of Scotland a poem on the demolition of what Dr. Stukely considered a Roman edifice, dedicated to Romulus; and, in a fit of resentment, the latter drew a caricature of Sir Michael carrying off a lapful of stones, with the devil goading him along, which was engraved by the Antiquarian Society of London.

In 1862, we were shown a very tasteful sketch of the O'on as it appeared immediately before it demolition, and the form it took was that of beehive. Gordon has given a very good illustration of it in his Itinerarium. It was a perfect dome, with a circular orifice at its apex, built in double courses of finely-hewn stones, laid on each other without mortar. Or, as Dr. Stukely say its shape is not unlike the famous Pantheon at Rome, before the noble portico was added to by Marcus Agrippa. Still, the building was small, to have been so famous. The perpendicular height, from the bottom to the top of the aperture, was 22 feet; the external circumference at the base, 88 feet; internal circumference, 61 feet; external diameter at the base, 2 feet; internal diameter, 19 feet 6 inches; circumference of the aperture, 86 feet 1 inch; diameter of the aperture, 11 feet 6 inches; height of the door from its basis to the top of the arch 9 feet; breadth of the door at the base, 6 feet inches; height, from the ground to the top of the key-stone of the door, 10 feet 6 inches breadth of the wall at the base, measuring at the door, 4 feet 3 inches; thickness of the wall where the arch springs, 3 feet 7 inches; and height of the basement on which the building stands, 4 feet 6 inches.

As to the builders of this structure, Nemus, a old monkish writer, argues for the Emperor Carausius; Hector Boece for Vespasian; Sir Robert Sibbald for Septimus Severus; and Dr. Stukely for Julius Agricola. If the initial letters J.A.M.P.M.P.T. were really engraved on a stone in this little temple, it may be considered not unlikely that they should bear this reading (Julius Agricola, Magnae Pietatis Monumentum Posuit Templum).

Antiquarians are also greatly at variance with respect to the purpose which the building was intended to serve. Stuart, in his Caledonia Romana, is of opinion that the word O'on may be no other than the Pictish term for a house, or dwelling, as we find that the words Pict-Oon denoted the Picts dwelling-place, or settlement. The prefix 'Arthur', he further holds, may be a corruption of some Attic word. Sir William Bentham, the learned author of the 'Gaul and Cimbrii,' suggests that the name 'Arthur's O'on' is probably derived from the old Gaelic words Art, a house, and Om, solitary, meaning a retired dwelling. Gordon takes the derivation from Ard nan Suainhe, the high place, or temple of the standards; as Arthur's Seat, Edinburgh, is Ard nan Saidhe, the hill of the arrow; and Arthur's Seir, between Ross and Moray, is Ard nan Seir, the height from which to launch ships. Dr. Stukely's theory, as to Julius Agricola having been the founder of the building, is perhaps the most reasonable of all; and if this is accepted, we cannot but regard the humble fabric as a sacellum, or little chapel, in which the vexilla, or ensigns of the legion, were kept. That it was never designed for public worship is plain from its dimensions. Gordon adds that it may have been also used as a mausoleum, or depository, for holding within its hollow basement the ashes of some illustrious Roman. But a truce to banter. We now know as much as ever shall be known of this interesting relic, interesting only on the page of history. Nothing is left us of the O'on but the memory of its existence, and the green sloping bank on which it stood. Demolished, too, for the repair of a petty dam-head. 'The pity of it, Iago; the pity of it.'