Within the horseshoe and close up to it stand the famous blue-stones, now twelve in number, but originally perhaps more.  These stones are not so high as the trilithons, the tallest reaching only 7-1/2 feet.  They are nearly all of porphyritic diabase.  It has often been asserted that these blue-stones must have been brought to Stonehenge from a distance, as they do not occur anywhere in the district.  Some have suggested that they came from Wales or Cornwall, or even by sea from Ireland.  Now, the recent excavations have shown that the blue-stones were brought to Stonehenge in a rough state, and that all the trimming was done on the spot where they were erected.  It seems unlikely that if they had been brought from a distance the rough trimming should not have been done on the spot where they were found, in order to decrease their weight for transport.  It is therefore possible that the stones were erratic blocks found near Stonehenge.

Within the horseshoe, and near its apex, lies the famous “Altar Stone” (A), a block measuring about 16 feet by 4.  Between the horseshoe and the outer circle another circle of diabase stones is sometimes said to have existed, but very little of it now remains.

The whole building is surrounded by a rampart of earth several feet high, forming a circle about 300 feet in diameter.  An avenue still 1200 feet in length, bordered by two walls of earth, leads up to the rampart from the north-east.  On the axis of this avenue and nearly at its extremity stands the upright stone known as the Friar’s Heel.

In 1901, in the course of repairing the central trilithon, careful excavations were carried out over a small area at Stonehenge.  More than a hundred stone implements were found, of which the majority were flint axes, probably used for dressing the softer of the sandstone blocks, and also for excavating the chalk into which the uprights were set.  About thirty hammer-stones suitable for holding in the hand were found.  These were doubtless used for dressing the surface of the blocks.  Most remarkable of all were the ‘mauls,’ large boulders weighing from 36 to 64 pounds, used for smashing blocks and also for removing large chips from the surfaces.  Several antlers of deer were found, one of which had been worn down by use as a pickaxe.

These excavations made it clear that the blue-stones had been shaped on the spot, whereas the sarsens had been roughly prepared at the place where they were found, and only finished off on the spot where they were erected.

What is the date of the erection of Stonehenge?  The finding of so many implements of flint in the excavations of 1901 shows that the structure belongs to a period when flint was still largely used.  The occurrence of a stain of oxide of copper on a worked block of stone at a depth of 7 feet does not necessarily prove that the stones were erected in the bronze age, for the stain may have been caused by the disintegration of malachite and not of metallic copper.