PRESIDENTIAL ADDRESS. 6 4 
mt ashe 1 
The very precision of this map reduces the theory on which it is based to a 
condition of unstable equilibrium. If glacial conditions were developed in 
India, Australia, and South Africa by a 70° movement of the crust, were the 
movements to and from its assumed position in Permian times so rapid that the 
glaciation of these widely separated areas appears to be geologically contem- 
poraneous? If such movements had occurred, instead of evidences of glaciation 
over a wide area at the same period, we ought rather to find that the glaciation 
in each of the widely separated points occurred during distinctly different 
geological periods. 
But that is not the only weak spot in the evidence. The Permian (or Permo- 
Carboniferous) glaciation of Australia took place on the east and south-east of 
the continent as well as in Western Australia, and the eastern ice-sheets would 
thus have been active within 30° of Professor Koken’s Permian equator. There 
are still three other serious pieces of colour-discord in this picture. In the 
State of Sio Paulo—that is, within Koken’s ‘ Permian’ tropics—Dr, Orville 
Derby has described beds which strikingly recall the features of the Upper 
Paleozoic glacial beds of India and South Africa. It is possible that these 
are due to the work of glaciers at a high level; but, since the publication of 
Professor Koken’s memoir, other occurrences of the kind have been described 
by Dr, I. C. White in different parts of Brazil, and there is a general 
correspondence between the phenomena in South America and those in the 
formations of the same age in the Indian, Australian, and African regions. 
Then, too, if we accept this expression of the physical geography during 
Upper Paleozoic times, we must carefully explain away the suspicious breccias 
and brockrams which have been regarded by many geologists as evidences of a 
cold climate during Permian times in the Urals, the Thuiringerwald, the English 
Midland and Northern counties, Devonshire and Armagh—places that would 
he on or near Koken’s ‘ Permian’ equator. Finally, we find the hypothetical 
Permian North Pole in a locality which has failed to produce any signs of 
glaciation. 
To attempt a discussion of the explanations offered to account for the great 
Upper Paleozoic glaciation would lead us far from the present theme. The 
question is raised merely to show that the phenomena are not consistent with 
the supposed movement of a solid shell over a solid core assisted by an 
intermediate molten lubricant. Geologists may be compelled to hand back the 
theory of a molten substratum to the mathematicians and physicists for further 
repair; but it does not necessarily follow that a foundation theory is unsound 
merely because it has been overloaded beyond its compressive strength. 
The extraordinarily great distances between the areas that show signs of 
glaciation in Permo-Carboniferous times form a serious stumbling-block to most 
of the explanations which have hitherto been offered. One is almost tempted in 
despair even to ask if it is not possible iat these fragments of the old 
Gondwana continent are now more widely separated from one another than they 
were in Upper Paleozoic times. It is a bold suggestion indeed that one can 
safely put aside as absurd in geomorphology. There is nothing else apparently 
left for us but the assumption of a general refrigeration. 
The idea of the greater inequalities of the globe being in approximately static 
equilibrium has been recognised for many years: it was expressed by Babbage 
and Herschel; it was included in Archdeacon Pratt’s theory of compensation ; 
and it was accepted by Fisher as one of the fundamental facts on which his 
theory of mountain structure rested. But in 1889 Captain C. E. Dutton pre- 
sented the idea ‘in a modified form, in a new dress, and in greater detail’; he 
gave the idea orthodox baptism and a name, which seems to be necessary for the 
respectable life of any scientific theory. ‘ For the condition of equilibrium of 
figure, to which gravitation tends to reduce a planetary body, irrespective of 
whether it be homogeneous or not,’ Dutton’® proposed ‘the name isostasy.’ 
The corresponding adjective would be isostatic—the state of balance between 
the ups and downs on the Earth. 
For a long time geologists were forced to content themselves with the con- 
clusion that the folding of strata is the result of the crust collapsing on a cooling 
1 Dutton, ‘On some of the Greater Problems of Physical Geology,’ Bull. 
Phil, Soc. Wash., xi. 53, 1889. 
