The chief interest of these tombs lies in the remarkable designs engraved on some of the stones of the passages and chambers.  They are fairly deeply cut with a rather sharp implement, probably a metal chisel.  They are arranged in the most arbitrary way on the stones and are often crowded together in masses.  There is no attempt to depict scenes of any kind, nor is there, indeed, any example of animal life.  In fact, the designs seem to be purely ornamental.  The most frequent elements of design are cup-shaped hollows, concentric circles or ovals, star-shaped figures, circles with emanating rays, spirals, chevrons, reticulated figures, parallel straight or curved lines.  There seems to be no clue as to the meaning of these designs.  They may have been merely ornamental, though this is hardly likely.

At New Grange, near Drogheda, there is a similar series of tumuli, one of which has become famous (Fig. 8).  It consists of a huge mound of stones 280 feet in diameter surrounded by a circle of upright blocks.  Access to the corridor is gained from the south-east side.  This corridor leads to a chamber with three divisions, so that corridor and chambers together form a cross with a long shaft.  The walls are formed of rough slabs set upright.  In the passage the roof is of slabs laid right across, but the roof of the chamber is formed by corbelling.  On the floor of each division of the chamber was found a stone basin.

[Illustration:  Figure 8.  Corridor-tomb at New Grange, Ireland (Coffey,
               Transactions of the Royal Irish Academy, 1892.)]

Around the edge of the mound runs an enclosure wall of stones lying on the ground edge to edge.  A few of these are sculptured.  The finest is a great stone which lies in front of the entrance and shows a well-arranged design of spirals and lozenges.  There are also engravings on one of the stones of the chambers.  These designs are in general more skilful than those of Lough Crew.  They consist mainly of chevrons, lozenges, spirals, and triangles.

The monuments we have so far described are all tombs.  Ireland also possesses several stone circles.  The largest are situated round Lough Gur, 10 or 12 miles south of Limerick.  There was at one time a fine circle west of Lough Gur at Rockbarton, but it is now destroyed.  On the eastern edge of the lough is a double concentric ring of stones, the diameter of the inner circle being about 100 feet.  The rings are 6 feet apart, and the space between them is filled up with earth.  In 1869 an excavation was made within the circle and revealed some human remains, mostly those of children from six to eight years old.