180 
ON MOVEMENTS IN ROCKS.* 
By G. W. LAMPLUGH F.R.S., F.G.S. 
(PLATES XI. and XI1.). 
WHEN man began to think of his surroundings he soon became 
impressed with the idea of the unchangeableness of rocks in 
this world of change. ‘ As firm as a rock’ has its equivalent 
in every language ; and from the very earliest times men have 
raised pillars of stone, unhewn or hewn, as memorials that 
should outlast all others. 
Until science undertook its critical scrutiny, the permanence 
of the ‘ everlasting hills’ went unquestioned ; and the geolo- 
gist had to do battle with many old prejudices when he first 
ventured to make known the truth that ‘ the hills are shadows, 
and they flow from form to form, and nothing stands.’ But the 
evidence being so clear and the facts so irrefragable, it has 
now sunk into common knowledge that, in regard to their 
surface aspect, the rocks have no stability, but are passing 
perpetually through cycles of change, and that the giant 
crags, so far from being eternal, are giants only because of their 
youth or immaturity. 
There are changes of a more intimate kind, however, that 
are not so conspicuous as these surface-phenomena, though 
they are equally well-known to geologists. They are the 
changes which have affected every particle of the rock through- 
out its mass, and have often so greatly modified its internal 
constitution or its structure that, under the cloak of apparent 
immobility, the rock may carry a history of interstitial move- 
ments almost as complex as a life-history, and far more pro- 
longed. As for the igneous rocks—the parents of all—that 
were once molten and have slowly become solid, it is recognised 
by every student how profound and intricate have been the 
re-actions in the magma, as in some vast cauldron charged 
with a flux of unlike substances, and how vigorous has been 
the interplay of particles, before the rock took form. 
Considering the far simpler sedimentary rocks alone— 
solidification with the ever-mysterious cohesion in its train, 
concretionary action, mineral replacements, metamorphism, 
folding, jointing, shearing, cleavage—all imply subtle creepings 
of the particles within the mass into new places and new rela- 
tionships under the play of forces of which we have as yet an 
imperfect comprehension. 
Of course, there is no such state known to us in Nature as 
absolute quiescence ; and it may be granted that rocks are rela- 
tively quieter than most objects on this unquiet earth. But I 
* Presidential Address to the Herts. Nat. Hist. Soc., Feb. 28th, 1911. 
Naturalist, 
