Edinburgh Geological Society. 009 
stable equilibrium is being attacked by causes acting with infinite 
slowness—it is because of this that a time always comes, and must 
come with varying degrees of suddenness, when the pre-existing 
equilibrium is overthrown. Then come what we are pleased to call 
catastrophes, and which may be so to us, but which are all inseparably 
connected with the perfect continuity of causes, and the slow accu- 
mulative effects of their mvisible and ceaseless operation. Do we not 
know this by experience in the little sphere of our own creations ? 
In many of the ancient palaces of our fathers it was the fashion to 
decorate the ceilings with flowers and fruits, often cast in massive 
moulds, and suspended over our heads by means adequate to secure 
stability. And so they will remain, and have remained for centuries. 
But the slow continuities of physical causation have never ceased to 
work, and bit by bit operations as slow as any ever conceived by 
Hutton or by Lyell have been steadily undermining the conditions 
of that stability, until at last m one moment of time the whole 
mass is precipitated upon the floor, to the imminent danger of many 
lives. I am not drawing on my fancy for this illustration. It 
actually happened in a’ case I knew—a case in which many 
persons had a narrow escape from death or from serious injury. 
There are innumerable other cases of sudden violent action being 
the inevitable result of the slow continuity of causation. The great 
tidal wave which accumulated a few years ago in the Bay of 
Bengal, and which—invisible in that wide area—became terribly 
visible in the Hoogly and the Ganges—drowning in a few minutes 
of time thousands of the teeming population. The breaking up of 
the ice on the great frozen rivers of North America and of Northern 
Asia is an annual catastrophe, the magnitude and magnificence of 
which has been often described. The rending of ice-cliffs on the 
coast of Greenland, and the launching of monstrous icebergs upon 
their majestic voyages to the south, is another of the superficial 
catastrophes which are seen by few, but has always vividly impressed. 
those who have been so fortunate as to see that sudden result of slow 
causation. Similar phenomena on a still grander scale take place 
in the Antarctic Circle, when whole miles of ice-cliff break off from 
the great southern barrier, and float in vast islands, probably for many 
years, round that tempestuous ocean. And yet the forces which are 
ever acting in cases such as these are weak and local in comparison 
with the tremendous energies which are at work, as we have every 
reason to believe, under that crust of the globe upon which we stand. 
The usual illustration of these energies, the example of which is con- 
tinually referred to, is that of voleanic action. And no doubt we may 
well refer to it, for perhaps never in historic times, and perhaps never 
in pre-historic times, have outbursts of volcanic energy been more 
tremendous than they have been during the time in which we are now 
living, nay, even during the single year which is drawing to its close. 
And yet I think we may say with absolute conviction that the energy 
of volcanoes is not the most deep-seated or the most tremendous of 
which geology must take account. The movements which have given 
a definite direction of dip and strike to the whole masses of sedimen- 
tary deposits, occupying an extcnsive region—such, for example, as 
