“The large monoliths of the outer circle, and the trilithons of the horse-shoe are all sarsens. [See general plan, Fig. 15.] These sarsens in their composition are sandstones, consisting of quartz-sand, either fine or coarse, occasionally mixed with pebbles and angular bits of flint, all more or less firmly cemented together with silica. They are the relics of the concretionary masses which had become consolidated in the sandstone beds that once overlaid the chalk of the district, and had resisted the destructive agencies by which the softer parts of the beds were removed in geological times. They range in structure from a granular rock resembling loaf sugar in internal appearance to one of great compactness similar to and sometimes passing into quartzite. “The monoliths and trilithons all consist of the granular rock. The examples of the compact quartzite variety, of which many were found in the excavations, were almost without exception either hammerstones that had been used in shaping and dressing the monoliths, or fragments which had been broken from off them in these operations. “The small monoliths, the so-called ‘blue stones,’ which form the inner circle and the inner horse-shoe, are, with the undermentioned exceptions, all of diabase more or less porphyritic. Two are porphyrite (formerly known as felstone or hornstone). Two are argillaceous sandstone. “Mr. William Cunnington, in his valuable paper, ‘Stonehenge Notes,’ records the discovery of two stumps of ‘blue stones’ now covered by the turf. One of these lies in the inner horseshoe between Nos. 61 and 62, and 9 feet distant from the latter. It is diabase. The other is in the inner circle between Nos. 32 and 33, 10 feet from the former, and consists of a soft calcareous altered tuff, afterwards designated for the sake of brevity fissile rock. “The altar stone is of micaceous sandstone.” I now come to the second point, to which I shall return in the next chapter. In studying the material obtained from the excavations, it was found in almost every case that the number of chippings and fragments of blue stone largely exceeded that of the sarsens; more than this, diabase (blue stone) and sarsen were found together in the layer overlying the solid chalk (p. 15). Chippings of diabase were the most abundant, but there were few large pieces of it. Sarsen, on the other hand, occurred most abundantly in lumps (p. 20); very few small chips of sarsen were found (p. 42). Hence Prof. Gowland is of opinion that the sarsen blocks were roughly hewn where they were found (p. 40); the local tooling, executed with the small quartzite hammers and mauls, would produce not chips but dust. [Illustration: FIG. 20.--Showing the careful tooling of the Sarsens.]