206 W. R. BROWNE, 
from a depth and flow to the surface. Although at present 
only one spring—a chalybeate one—is actually flowing, it 
is only of recent years that the spring which is the source 
of the present supplies has ceased to flow, and there is 
evidence that in the past quite a number of springs were 
active. A considerable amount of travertine has been 
deposited from these springs, and is still being formed. 
So far the deposit has a maximum depth of 12 feet, and is 
said to cover an area of D acres. Hxcept at one point 
where the creek takes a sharp bend to the east, the traver- 
tine is wholly on the east or right bank of the stream. The 
Rock Flat Springs are at the base of a great quartzitic 
outcrop, from which the place takes its name. The out- 
crop consists of sandstone on edge, intersected with quartz 
veins, and which merges into quartzites towards the 
west, and ultimately into a kind of quartz breccia, the 
cementing material being also quartz. The dip of the 
quartzite is about W. 10° S. at 40°. 
Travertine is found sparingly developed in other parts of 
the region; it has been noted along the Bobundarah Road 
near the North Brother, also just south of Bunyan along 
the Sydney Road. It occurson top of the old metamorphic 
rocks, and is generally covered by alluvium. Probably it 
is post-Tertiary in age. 
A curious occurrence was found in Butler’s Creek, a bit 
north of Mittagang Bridge. Here the creek, when running, 
tumbles over a rock-bar about 12 feet high, and down the 
face of this there is a kind of stalactitic deposit of traver- 
tine, evidently formed when only a trickle of water was 
running, and due to evaporation as the water flowed over 
the heated rock in summer. 
River gravels.—Perhaps the most extensive development 
of these is along the Numeralla Road to the west of the 
‘Toll Bar Bridge over Rock Flat Creek. The gravels com- 
