334 
PROCEEDINGS OF SECTION C. 
stratum in question, the problem is solved, whether the water-bearing 
stratum, when mapped out, form a circle and the stratum be con- 
tinuous within the limits of the circle, like a porous earthenware 
saucer sunk in clay, or whether, on the other hand, the stratum die out 
when traced along its outcrop or followed down the dip into the bowels 
of the earth. In the latter case the stratum is simply a pipe of more 
or less irregular sectional area, which the bore converts into an inverted 
syphon. In a clear syphon the water would rise with all the force due 
to the pressure of the head of water; but a syphon closely packed with 
sand is not only a syphon but also a filter, and in proportion to the 
openness or compactness of the sand the flow will he strong or feeble. 
In mapping the eastern limit of the Lower Cretaceous formation, 
we find that at the base there is a series of soft, gray, very friable 
sandstones, grits, and conglomerates. This sandstone absorbs water 
with avidity. The rock is, moreover, so destitute of cement, or it may 
he that the cement is so soluble, that a lump of it on being saturated 
with waterfalls away to a heap of sand. We can therefore under- 
stand how, underground, where such strata are saturated with water, 
they may be correctly described by the drillers as “ sand ” instead of 
“ sandstone.” To this rock we felt it necessary to give a distinctive 
name, the “ Blythesdale Braystone,” as it is well developed atBlythes- 
dale, near Roma, and somewhat resembles a sandy rock much in demand 
in the west of Scotland, under the name of braystone, for holystoning 
and scrubbing purposes. 
This sandstone is first met with near the New South Wales 
border, at Whetstone, on the Maciutyre River. The exigencies of 
travel took us down the Macintyre to (xOondiwindi, and up the Weir 
River, where nothing but alluvial soil is met with till we reached 
Tarewinnaba, on the Weir. At this point the braystone is first seen, 
and is at once covered by the Desert Sandstone. A cake of Desert 
Sandstone extends from this point north, east, and west. The eastern 
and northern margins of this tableland were traced, and it was found 
that the Desert Sandstone overlaps the Ipswich Coal Measures, which 
arc exposed in several places where the Condamiue has cut through 
the overlying Desert Sandstone. On the north-western margin of 
this tableland, near Surat, the Desert Sandstone directly overlies the 
upper or shaly beds which give rise to the Rolling Downs, and which 
form by far the greater proportion of the strata of the Lower 
Cretaceous formation, so that the Blythesdale Braystone may be 
assumed to crop up beneath the Desert Sandstone somewhere between 
Dogwood Creek and Wieonbilla Creek. At Bendemere, on Yeulba 
Creek, the Desert Sandstone having been denuded by the stream, the 
upper shaly Rolling Downs Beds are directly in contact with strata 
understood to belong to the Ipswich Coal "Measures, and the non- 
appearance of the Blythesdale beds is accounted for by a “ fault.” A 
few miles to the west the Blythesdale braystones arc met with in 
great force, being succeeded to the north by the oider (supposed) 
Ipswich Coal Measures, and to the south by the newer shaly members 
of the Lower Cretaceous formation. As the braystone is traced north- 
westward by Blythesdale, Roma, Taboonbay, Donnybrook, Hogan- 
thulla, and the heads of the Warrego, its south-western edge merges 
into the downs formed by the shaly members of the Lower Cretaceous, 
and to the north-east it disappears under the Desert Sandstone (which 
