[Footnote 70: What Varro describes as the military fence of ditch and bank was doubtless the typical Herefordshire fence of modern England which Arthur Young, in _The Farmers' Letters_, recommends so highly as at once most effective and most economical. The bank is topped with a plashed hedge of white thorn in which sallow, ash, hazel and beech are planted for "firing." The fencing practice of the American farmer has followed the line of least resistance and is founded on the lowest first cost: the original "snake" fences of split rails, upon the making of which a former generation of pioneer American boys qualified themselves for Presidential campaigns, being followed by woven wire "made by a trust" and not the most enduring achievement of Big Business. The practical farmer, as well as the lover of rural scenery, has cause for regret that American agricultural practice has not yet had the patience to enclose the land within live hedges and ditches.] [Footnote 71: The kind of fence which Varro here describes as "ex terra et lapillis compositis in formis" is also described by Pliny (H.N. XXXV, 169), as formaceos or moulded, and he adds, "aevis durant." It would thus clearly appear to have been of gravel concrete, the use of which the manufacturers of cement are now telling us, is the badge of the modern progressive farmer. Cato (XXXVIII) told how to burn lime on the farm, and these concrete fences were, of course, formed with lime as the matrix. When only a few years ago, Portland cement was first produced in America at a cost and in a quantity to stimulate the development of concrete construction, engineers began with rough broken stone and sand as the constituents of what they call the aggregate, but some one soon "discovered" that the use of smooth natural gravel made more compact concrete and "gravel concrete" became the last word in engineering practice. But it was older even than Varro. A Chicago business man visiting Mycenae picked up and brought home a bit of rubbish from Schliemann's excavations of the ancient masonry: lying on his office desk it attracted the attention of an engineering friend who exclaimed, "That is one of the best samples of the new gravel concrete I have seen. Did it come out of the Illinois tunnel?" "No," replied the returned traveller, "it came out of the tomb of Agamemnon!"] [Footnote 72: Varro here seems to forget the unities. He speaks in his own person, when Scrofa has the floor.] [Footnote 73: It will be recalled that Aristotle described slaves as living tools. In Roman law a slave was not a _persona_ but a _res_. Cf. Gaius II, 15.]