480 NEW SOUTH WALES. 
of the district. I collected a few impressions of leaves descending 
into the Kangaroo Ground, which indicated that the coal series existed 
there, although there may be no beds of coal in the region. 
The sections examined do not seem to promise profitable explora- 
tions for coal in this district. ‘The beds are too thin to be worked. 
We cannot speak, however, with certainty of the Bulli region to the 
north of the part explored by us. The beds seem to be less produc- 
tive as we go south from Bulli. 
Fissures, and Concentric Structure. 
The fissures in the coal formation correspond in direction with 
those of the sandstone above, and in general have the courses north- 
northeast and west-northwest. Other directions are, however, met 
with. At Telegraph Hill, Newcastle, the fissures run northwest, and 
the same extend through the coal. One hundred rods to the south- 
ward there are two distinct lines of fissures, one east by north and the 
other north by west. Near the Bulli coal cliffs, there are two sys- 
tems, one north by east, and the other northwest by west. 
In some of the sandstone layers there are numerous and irregular 
fractures or seams, dividing the surface into small polygonal areas, 
which have a concentric structure, with walls bordering the seams. 
The walls are from half an inch to two inches thick, thus varying 
with the thickness of the layers or coarseness of the rock, and the size 
of the included areas. 
This structure is carried to the most minute perfection in the thin 
beds of ironstone. ‘The accompanying figure represents a fragment | 
from one of these beds. ‘The areas here are often less than a square 
inch, and the walls, which are double, 
as usual, rarely exceed a twelfth of 
an inch in thickness, and in some 
parts are but a twentieth. The speci- 
mens break in the line of the fissures 
between the walls with the feeblest 
stroke, falling into polygonal frag- 
ments, bounded on each side with 
smooth even surfaces. ‘The layer 
which afforded the specimen figured, 
averages two and a half inches in 
thickness, and extends over several 
