By Nevil Story Maskelyne, M.A., F.R.S. 159 
the rest of the ground-mass, and hardly atrace of the felspar then remaining un- 
decomposed. Some of these fragmentary crystal outlines may belong to other 
minerals, such as augite, but their forms are too much broken up for a decision 
as to the original character of the minerals, and so far as to the rock or rocks 
from which they may have been derived. The chlorite occurs sometimes in 
distinct green crystalline aggregations. 
No. 11. The stone presents a bluer aspect than the last described, due to its 
containing more of the grey-green chlorite: the felspar is more abundant in 
fragmentary crystals and it is less completely decomposed than the stone num- 
bered 9. The waved and so-termed fluxional nature of the ground-mass which 
has the appearance of having flowed round and past the less mobile fragments 
of felspar crystals is very marked in this stone. 
No. 17. The ground-mass of this stone is of fine grain and the fluxional 
structure is very prevalent. The stone is remarkable for the large amount of 
pyrrhotine (‘‘ magnetic pyrites”) it contains, to the decomposition of which 
the brown stain that discolours it is due. The structure of the rock is evidently 
schistose. 
No. 19. Coarser in the grain of its ground-mass, this stone is less remarkable 
for the fluxion-structure than No. 11 and No. 17. The Chlorite in it is more 
frequently vermicular in character than in the other stones. In a section made 
from it, is seen, associated with the felspathic fragmentary crystals, an angular 
fragment of a decomposed fine-grained doleritic rock. 
A description of the Stonehenge stones would be incomplete that 
omitted to notice the large numbers of chips or fragments that Mr. 
Cunnington has shewn may be found by searching beneath the 
surface soil immediately round the great circle of stones, and more 
especially on the south and west sides of it. Their lithological 
features are generally identical with the stones that compose Stone- 
henge, large numbers of them being fragments of the same kinds 
of diabasic dolerite and felsitic rock that form the materials of the 
smaller obelisks. Some of them on the other hand present somewhat 
distinctive features: thus, in particular, there may be found among 
them a compact variety of rock with a decided slaty cleavage and 
character, a quartzose grit with thin scales of brown mica and 
green grains of, apparently, chlorite. In one of them belonging 
to the felsitic kind of rock composing the four obelisks, one of the 
fragments of felspar-crystal exhibits the twin-striation of an anorthic 
felspar, probably of oligoclase. An extension of the search thus 
commenced by Mr. Cunnington would undoubtedly lead to a much 
_ More complete acquaintance with the nature of the stones employed 
_ at Stonehenge, and aid in a future solution of the problem of their 
