Who

What

How

When

Where

Why

Pots & Basins

Quartz

Art

 

Cairns B & F at Carrowkeel. Photo © Leo Regan.

How Were They Constructed?

One of the most fascinating questions about ancient structures is how were they built? When you survey the ancient monuments of the world (Graham Hancock's and Robert Bauval's recent books are interesting places to start), obviously the chambered cairns are of a different order to monuments such as the Giza pyramids, mesoamerican structures and Indian temples. For a start they are always round, while many other cultures built in square shapes. The size of volume of stones used to build Irish monuments are much smaller than those used at sites such as Giza (some 6 million tons in The Great Pyramid).

The Irish used unhewn stone; most of the older cairns are constructed from river rolled stones or quarried limestone. While the type of stone used in construction of chambers is sometimes cut and trimmed and those used in the kerb are often one large stone split in two, they rarely exceed 4 tons in weight. The builders often went to great lengths to source the right materials. For example, the Boyne Valley and probably the Loughcrew builders travelled to the Wicklow Mountains to obtain quartz, then known as Sunstone, to cover their temples, while those at Carrowkeel and Carrowmore gathered theirs in the Ox Mountains.

The Boyne Valley builders took great care in the construction of their mounds. The Chambers and Kerbs would have been built first, but only after many years of painstaking observations of the cycles and motions of the heavens. When the chamber orthostats were in place, before the roofstones were added, the kerb would have been laid out and would have acted as a kind of symbolic or artificial horizon.

When the passage and chamber of Newgrange were covered over, the builders carved grooves on the upper surfaces of the stones to channel off water and keep the interior dry. Several of the slabs used in roofing were engraved before being set in place, most notably the marvellous ceiling of the right hand recess at Newgrange. The chamber is corbelled, which means that each layer of stones added by the roofing gang overlapped the last by several inches. The corbels were tilted, like our slate roofs, again to allow the water to run off, and they were packed with small stones known as spalls.

The building of the actual cairn was the last part of the process. The chamber of Newgrange was covered in a small cairn which reached to the capstone. This would have greatly stabilised the structure. Then the cairn proper was built - again a complex affair. Turves were stripped from the surrounding area and the cairn material was carefully built up in alternate layers of stone, rubble and organic material.