428 T. W. E. DAVID. 
hypothesis be adopted, the model exhibited might serve as an 
explanation. It has the form of a bent pipe with the convexity 
downwards, like an inverted siphon in shape, with the short leg 
however placed upperinost, so that following the gradient of the 
pipe from the highest point downwards, the curve is at first steep 
then more gradual to imitate the curve of the Cretaceous strata 
as they dip off the impervious Paleozoic and Mesozoic Rocks, 
forming the axis and foothills of the Main Dividing Range, into 
the Western Plains. The lower end of the pipe is filled with sand, 
then succeed coarse lead shot, and lastly marbles, this arrange- 
ment being intended to imitate the decreasing porosity of the 
water-bearing beds of the Rolling Downs Formation as they recede 
from the foothills of the Main Dividing Range towards the 
Western Plains. Three glass tubes ascend vertically from the 
pipe, tapping respectively the parts of the pipe filled with sand, 
shot, and marbles. Water coloured by permanganate of potash 
is now poured in at the upper end of the pipe until the pipe is 
filled, and the water at once begins to ooze out through the sand 
at the lower end of the pipe, to replenish which loss more water 
is being continually added at the upper end of the pipe. It will 
be observed that the water gradually ascends each of the three 
vertical glass tubes, which communicate at their lower ends with 
the lead pipe, until the water eventually becomes stationary at a 
certain level in each of the tubes. A line drawn from the point 
of intake through these points in the glass tubes to the point 
of outlet represents the hydraulic grade, and it will be noticed 
that under the conditions arranged, the hydraulic grade has the 
form of a convex curve (the convexity uppermost). Ifthe artesian 
basin of Australia be hydraulic rather than hydrostatic, the 
hydraulic grade would probably have the above form, and conse- 
quently very little fall might be expected in the hydraulic grade 
near the central portions of the basin. 
In writing these notes the author would express his special 
indebtedness to the valuable report accompanied by map and 
sections prepared by Mr. J. B. Henderson, and to the similar 
