TRANSACTIONS OF SECTION C. 381 
The researches of Dutton, Hayford, Bowie, Gilbert, and others appear to 
have placed the doctrine of isostatic compensation upon a firm basis; neverthe- 
less, the operation of the adjustments does not appear, as yet, to be understood, 
and it is probable that cognisance has not been taken of all the factors. 
In the example cited, of the elevation of both the Great Mesozoic peneplain 
and a great portion of the loaded offshore area, it seems difficult, under the 
doctrine of continuous compensation, by erosion and sedimentation, to explain, 
in the first place, how the positive element could remain, for ages, in the one 
general position of equilibrium, while the offshore area was being loaded; and, 
in the second place, how the elevatory movement could have received its initial 
impetus, especially as the effect appears greater than the cause if it be assumed 
that the Cretaceous sedimentation gave rise to the Tertiary uplifts. On the 
other hand, the foundering of suboceanic areas in the neighbourhood might be 
adduced as an explanation, but the evidence is not at all conclusive on this 
point, 
; The history of the revivals of elevation during Tertiary time over Eastern 
Australia indicates crustal adjustment by jumps, and in this case also the 
increasing amount of vertical movement suggests that the elevations of the 
plateaus more than compensate for the erosion sustained in these regions during 
recent geological time. 
The extrusion of the basalts is in harmony with the doctrine, but the 
action appears to have been catastrophic, rather than gradual, in nature. 
The sequence of geographical forms cited suggests that sedimentation in- 
fluenced the formation of plateaus only in a minor degree, but, on the other 
hand, that stresses accumulated gradually within the zone of compensation, until 
a belt of weakness, or mobility, was established by means of which the ill- 
adjusted portions were connected. Upon the arrival of such a stage adjustment 
ensued with relative rapidity with the production of epeirogenic uplifts and 
depressions. This neither denies the ability of a load, such as a mass of sedi- 
ments, or an Ice Cap, to depress the underlying region, nor does it seek to 
exclude the tendency for an unloaded area to rise; it merely assigns to such 
geet a subordinate part in the shaping of the greater features of the Earth’s 
crust. 
It is probable also that an analysis of a series of gravity measurements 
which may he taken hereafter in Australasia would reveal the existence therein 
of gravity anomalies, and it is probable also that the disposition of these would 
be other than those which might have been inferred from a mere inspection 
of the topography. 
5. The Melallogenetic Provinces of Eastern Australia. 
By C. A. Sussmincn, 
6. New Rvidence for Darwin’s Theory of Coral Reefs. 
By Professor W. M. Davis. 
7. The Genesis of the Diamond in New South Wales. By L. A. Corton. 
8. The Occurrence of Spilitic Lavas in New South Wales. 
By W.N. Benson. 
9. Structural Features of the Coal-fields of Pennsylvania and their 
Influence on the Origin of Hard Coal. By Professor E. 8. Moorr 
M.A; Ph.D. y r B.S. Moore, 
There are two main coal-fields in Pennsylvania, the Bituminous and the 
Anthracite. The latter field comprises an area of approximately 480 square miles 
situated in the highly folded portion of the Appalachian Province, while the 
