The fosse of the Wall and Vallum at this point deserve attentive examination. In passing over the crown of the hill, they have been excavated with enormous labour out of the basalt of which the summit consists. The workmen, as if exhausted with the task of raising the splintered fragments, have left them lying on the sides of the moats. A mass on the outside of the north ditch, though now split by the action of the frost into three pieces, has evidently formed one block, and cannot weigh less than thirteen tons. It is not easy to conceive how they managed to quarry so tough a rock without the aid of gunpowder, or contrived to lift, with the machinery at their command, such huge blocks. No luis-holes appear in them. The lithograph presents a view of the giant works of the Vallum and fosse at this point. It is quite evident that here, at least, the north agger did not form the Military Way. There are several breaks and irregularities in both the mounds; the works have probably been left by the Romans in a rough, unfinished state. Between this spot and the craggy summit on which Sewingshields farm-house is perched, the ground is flat, and destitute of any decided descent to the north. On this account, and for mutual defence, the lines of the Barrier keep close together, so close, sometimes, as scarcely to leave room for the passage of the Military Way between them. [Sidenote: PROCOLITIA.] PROCOLITIA is the seventh stationary camp on the line of the Wall. It was garrisoned by the first Batavian cohort, which, with two others from the same country, and the two Tungrian cohorts, was with Agricola in his great battle with Galgacus in the Grampian Hills. That the ruined camp at Carrawburgh was the adopted home of this cohort, is proved by the altar engraved on page 62, and by [Illustration: Slab—Coh. I. Batavorum] the fractured slab now introduced,[94] and which was found here in the year 1838. On this mutilated stone, the words COH I BATAVORVM are quite distinct, and are of themselves sufficient, not only to fix the site of the ancient PROCOLITIA, but to corroborate the testimony of Tacitus, on the presence of Batavians in Britain during the period of Roman occupation. The line following may probably be read INST[ANT]E BVRRIO, and bears the name of the prefect under whose superintendence the building was erected, to which the slab referred. In the last line, the word CO[RNELIANO may be perceived. In 237, when Maximinus was emperor, Titius Perpetuus and Rusticus Cornelianus were consuls. That this is the date of the inscription is rendered likely from a fragment of this emperor’s name appearing in the beginning of it. Whitaker gives, as the meaning of the word PROCOLITIA, the ‘fortress in the woodlands.’ In the Gaelic tongue, _coille_ signifies a wood.