560 Reports and Proceedings—Duke of Argyll’s Address. 
the dip and direction of the rocks which are so marked in the geogra- 
phy and geology of Scotland north of the Clyde—those movements, 
again, which have broken and bent, so as even to bend over and re- 
duplicate, the beds round the flanks of the Alps—those, again, which 
have occasioned immense faults, such as that which marks the deep 
line of the Caledonian Canal—these are forces evidently far deeper- 
seated and far more powerful than any, even the greatest, which find 
their vent in the raising or destruction of voleanic cones. And if, in 
the action of these greater and more deep seated forces, the same law 
has prevailed as that which we know to have prevailed in the action 
of volcanic heat, then we may be certain that the slow, majestic con- 
tinuity of physical causation has been compatible in this case also with 
what we call catastrophes—that is to say, with the occurrence of mo- 
ments of accumulated effects. Andas the outbursts of a volcano are only 
the sudden revelation of causes which have long been silent, but have 
never ceased to work, so it is reasonable to suppose that like sudden 
revelations have been made from time to time of those more central 
forces operating on the crust of the globe, which are even more con- 
tinuous and more unsleeping, and of which volcanic heat and volcanic 
outburst are but the local symptoms and effects. The truth is, that, 
when we come to look closely into the matter, it becomes evident that 
nothing can be more unphilosophical than the antithesis and opposition 
which is set up between what is called the law of continuity and 
what is called the doctrine of catastrophes. Thoughout all nature, and 
throughout all those operations of the human intellect which depend 
on the manipulation of natural forces, we see the two doctrines to be 
perfectly harmonious—strains and tensions maintaining themselves in 
absolute silence up to the bending or the breaking point—pressures_ 
pressing with tremendous but noiseless energy up to the bursting 
point—and then moments of rapid and sometimes of instantaneous 
change; change as dreadful as that which comes in the spring and 
roar of the tiger—this is the usual sequence of events—this is the 
rule and law which seems to govern all things around us; aye, and 
very often all things that we depend upon within us too. For every 
physician knows the terrible continuities of disease—how the thinning 
of the walls of vessels, and the weakening or degeneration of other 
organic tissues, go on, often unseen and unsuspected, until their 
appropriate result emerges in some catastrophe which destroys in a 
moment of time the reason or the life. And if it is irrational to quote 
the continuity of nature as affording any, even the least, presumption 
against sudden and great effects, it is still more irrational to quote it 
as irreconcilable with effects which, though catastrophes to us, whose 
scales of measurement are often the scales of pigmies, are in reality 
nothing but movements of infinitesimal magnitude in the scale of 
nature. I remember well hearing the late Principal James Forbes 
describe the impression made upon him by seeing a total eclipse of 
the sun from the top of a high tower upon a hill near Turin. We all 
know that the light of the solar disc is so intense that the deep shadow 
of an eclipse does not make itself apparent till every fragment of that 
intense surface has been shut out from shining, till, in short, the 
moment of “totality,” and how, consequently, the maximum effect 
