Post-and-Lintel and Corbel Construction
Of all the methods for spanning space, post-and-lintel construction is the simplest. At its most basic, two uprights (posts) support a horizontal element ( lintel ). There are countless variations, from the wood structures and underground burial chambers of prehistory, to Egyptian and Greek stone construction, to medieval timber-frame buildings, and even to present-day cast-iron and steel construction. Its limitation as a space spanner is the degree of tensile strength of the lintel material: the more flexible, the greater the possible span. Another early method for creating openings in walls and covering space is corbeling, in which rows or layers of stone are laid with the end of each row projecting beyond the row beneath, progressing until opposing layers almost meet and can then be capped with a stone (capstone) that rests across the tops of both layers.
Many megalithic tombs are preserved in Europe, where they were used for both single and multiple burials. In the simplest type, the dolmen , a tomb chamber was formed of huge upright stones supporting one or more table-like rocks, or capstones , in a post-and-lintel system. The structure was then mounded over with smaller rocks and dirt to form a cairn or artificial hill.
More elaborate burial sites—called passage graves —have corridors leading into a large burial chamber. At Newgrange in Ireland, a huge passage grave—originally 44 feet tall and 280 feet in diameter—was constructed about 3000–2500 bce ( fig. 1–12 ). Its passageway, 62 feet long and lined with standing stones, leads into a three-part chamber with a corbel vault (an arched structure that spans an interior space). Some stones are engraved with linear designs, mainly rings, spirals, and diamond shapes. These patterns may have been marked out using strings or compasses, and then carved by picking at the rock surface with tools made of antlers. Recent analysis of such engraved designs suggest that we should understand them in terms of the neuropsychological effects—including hallucinations—they would have had on people visiting the tomb. They may have played important roles in ritual or political ceremonies that centered around death, burial, and the commemoration and visitation of the deceased by the living.