on the Upper Wollondilly. 53 
In the first instance mentioned, the width of the dyke is stated 
to be 47 yards; its dip, 50°south-west; and its strike, south 22° 
east. Alternations of quartz rock and crystalline white and grey 
marble compose this dyke; innumerable lines and scratches mark 
the edges and face of the marble; and the quartz has also been 
subject to a semicrystalline action, the surface being crumpled or 
doubled up into parallel anticlinal ridges.” There appears to be 
no line of demarcation traceable between the quartz and marble; 
and the two together, after descending into the bed of the river, 
suddenly curve round and re-enter the granite as a second dyke. 
Traces of green carbonate of copper are found associated with 
the other minerals of this dyke. 
The author considers that the scratches and furrows which he 
has observed, and other phenomena in the line of dip, could not 
have been in existence before the formation of the present river 
channel. 
A second dyke is then described, in a place where the rocks 
are thrown into great disorder, and the author details some 
changes which have produced singular conditions of mineral 
structure. He also supposes that they exhibit marks of a gra¬ 
dation existing between limestone and quartz. A third dyke of 
the same character is then mentioned, in which the constituents 
of the granite are mixed up with the calcareous rock ; and the 
author states, that, near these dykes, the granite assumes a dis¬ 
tinct character, a greater proportion of felspar, and less mica, 
being present. 
At Jaoramin, higher up the river than the spot just alluded to, 
the structure of the rocks is described as somewhat different, the 
felspar being less completely mingled with the other minerals, but 
the rock occasionally passing into porphyry. Where it is not 
denuded, the rock, however, is here overlaid by a mass of con¬ 
glomerate, from 200 to 300 feet thick, through which the river 
makes its way. At St. Peter’s are low hills, more decidedly 
granitic. Tv ear Stuckey s farm are numerous fragments of crys¬ 
talline rock, the surface of which is much worn, as is the case 
with other calcareous rocks all over New South Wales. No 
traces of fossils have been found in these limestones. 
