There are usually four varieties: those of cut stone, as in the country around Tusculum; those of burned brick, as in Gaul; those of unburned brick as in the Sabine country; those of gravel concrete,[71] as in Spain and about Tarentum." _b. Monuments_ XV. Lacking fences, the more discreet establish the boundaries of their property, or of their sowings, by blazed trees, and so prevent neighbourhood quarrels and lawing about corners. Some plant pines around their boundaries, as my wife did on her Sabine farm, or cypresses, as I have on my property on Vesuvius.[72] Others plant elms, as many have done in the district of Crustumeria: indeed, for planting in plains where it flourishes there is no tree which can be set out with such satisfaction or with more profit than the elm, for it supports the vine and so fills many a basket with grapes, yields its leaves to be a most agreeable forage for flocks and herds, and supplies rails for fences and wood for hearth and oven. "And now," said Scrofa, "I have expounded my four points upon the physical characteristics of a farm, which were, its conformation, the quality of the soil, its extent and layout, its boundaries and their protection." _Of the considerations of neighbourhood_ XVI. It remains to discuss the conditions outside the farm itself, for the character of the neighbourhood is of the utmost importance to agriculture on account of the necessary relations with it. There are four considerations in this respect also, namely: whether the neighbourhood bears a bad reputation; whether it affords a market to which our products can be taken and whence we can bring back what we may require at home; whether there is a road or a river leading to that market, and, if so, whether it is fit for use; and fourth whether there is in our immediate vicinity any thing which may be to our advantage or disadvantage. Of these four considerations the most important is whether the neighbourhood bears a bad reputation: for there are many farms which are fit for cultivation but not expedient to undertake on account of the brigandage in the neighbourhood, as in Sardinia those farms which adjoin Oelium, and in Spain those on the borders of Lusitania.