160 Stonehenge: the Petrology of its Stones. 
sources. Whether the stones that thus strew the ground around 
Stonehenge are as Mr. Cunnington supposes, the scattered chips 
left by the artificers of the great monument after hewing and shaping 
the obeliskoid stones out of ruder blocks, or whether they are the 
fragmeuts left by despoilers who have broken up and shaped:into 
building stones the obelisks, the places of which within the circle of 
Stonehenge are now vacant or also other outer rows of them that 
have vanished altogether, it may now be impossible to determine. 
In the former case their position would seem to indicate that the 
stones of this class were brought on to the ground from south or 
south-west. 
The original monastic buildings at Amesbury and the walls of 
Old Sarum might have revealed something on the point suggested 
—but they too have been in turn despoiled, ae razed, all but* 
fragments of them. 
The plate represents the appearance of the different rocks of which 
Stonehenge is formed, when seen in a microscope with a low power 
(a one-inch object glass). The section No. 1 is that of one of the 
sarsen stones, No. 2 is the altar-stone, Nos. 3 and 4 are sections from 
the diabasic dolerite of the stones No. 4 and No. 20 respectively. 
In them A represents the Augite; F the felspar; X, chlorite; and 
Q the distinct crystals of quartz. No. 4 is a section of a rock closely 
resembling the diabase, from the Corstorphine Hills near Edinburgh ; 
the only rock yet met with by me that resembles in its microscopic 
characters this variety of the Stonehenge stones. No. 6 is a repre- 
sentation of a section of the felstone No. 17. It-shews well the 
fluxional structure of the rock, and is selected on account of its 
including a formless fragment of another rock. 
