52 
On Dykes of Marble and. Quartz 
The Wollondilly, however, from its source to its junction with 
the Uringalla (except near Towrang), is described by the author 
as running through igneous and metamorphic rocks, which are 
laid bare over a considerable area between the Cockburndoon, the 
Derra, and the Uringalla rivers, where recent volcanic outbursts 
have disturbed the older rocks. The sedimentary rocks wrapt 
round the margin of this area, the beds dipping at a considerable 
angle. 
On the north banks of the river, at a place called Jaoramin, 
beds of conglomerate are described, containing fragments appa¬ 
rently of transition rock; and the author considers, from the 
condition and appearance of the river banks, and the fact that a 
wide space, at a considerable height above the water, is covered 
with the debris of these conglomerates, that a considerable change 
of level has taken place in the district, producing elevation. 
Having given a general account of the district, the author then 
proceeds to describe the different plutonic rocks found in it, and 
states that they consist of syenite, syenitic granite, protogene, 
and porphyritic rocks of various kinds, and of greenstone, basalt, 
and trachyte,—all, with the exception of the three latter, passing, 
by regular gradations, from one to another. The syenites are 
said to resemble those of Skiddaw, and the syenitic granite that 
of Guernsey ; while a protogene is described greatly resembling 
a beautiful rock of the same kind in St. John’s Vale, near 
Keswick. 
At Arthursleigh, the author describes a spot where the face of 
an exposed cliff exhibits a net-work of quartz veins, with dykes 
of syenitic rock and hornstone; and not far off, a dyke of iron¬ 
stone, and others of basaltic rocks, amongst which are some 
injected trachytes, that have been used for building purposes. 
Having described the position and mineral character of these 
igneous rocks, as they appear en masse, the author then proceeds 
to allude to some singular instances of intrusive dykes of lime¬ 
stone and marble, at a spot known as “ Campbells,” or “ Shep¬ 
herds,” situated on the estate of Arthursleigh, just alluded to. 
These dykes occur in contact with hard, large-grained, grey 
syenite, and were seen on the right bank of the river Wollondilly. 
