Geological Society. 385 
spot to the south of Stockholm I saw what appeared to me a con= 
elusive proof of an alternate rising and sinking of the same land since 
this region was inhabited by man, first a depression of the ground 
of at least 50 feet below its former level, and then a re-elevation of 
the same amounting to at least 50 feet. 
The probable cause of the prolonged and insensible movements 
of large masses of land opens a wide and inviting field for specu 
lation. As we know that volcanic action is never dormant in some 
parts of the interior of the globe, it seems most natural to imagine 
that an alternate expansion and contraction of the earth’s crust may 
arise from a gradual increase or diminution of its temperature. 
Mr. Babbage has suggested that as many common kinds of stone 
have been shown by experiment to augment in volume when heated, 
and decrease in bulk when slowly cooled, a great thickness of sub- 
jacent rock may cause the surface to rise or sink according to the 
variations experienced in the subterranean temperature. We have 
also to consider the effects which might result from the slow cool- 
ing and crystallization of large reservoirs of melted matter, on 
which subject we have unfortunately as yet few experiments to 
guide our conjectures. We know not, for example, whether the 
passage from a fluid to a solid state would uplift or let down an 
incumbent mass of rock. A dense fluid, subjected to immense 
pressure, may, perhaps, on crystallizing into a rock like granite, oc~ 
cupy more space in its state of solidiry. Imeed not remind you 
that as ice floats in water, soa bar of cast iron floats on the surface 
of melted iron. 
But however obscure the origin of the movements in question, 
their reality if admitted affords a key to the interpretation of a va- 
riety of geological appearances, some of which I shall now proceed 
to consider. 
Dr. Beck has mentioned that the oldest strata in Denmark are 
often covered by deposits of gravel, sand, and loam, several hun- 
dred feet thick, in which, but more commonly upon them, lie erratic 
blocks. The sand and gravel beds rarely contain any fossils, but 
when shells do occur they are absolutely identical with living species. 
He has also found, in the lower valleys of Jutland, more than se- 
venty species of shells now living in the German Ocean. These 
facts agree precisely with others which I observed in different parts 
of Sweden, and which J have described in the memoir before al- 
luded to. On the west coast, between Uddevalla and Gothenborg, 
the beds of sand, gravel, and clay, containing recent oceanic shells, 
are seen at various heights from 100 to 300 feet above the sea. 
M. Alex. Brongniart formerly pointed out those which rest on the 
gneiss, near Uddevalla, and like him I saw Balani still attached to 
the rocks at the height of more than 150 feet above the sea-level. 
I ought, however, to state that at the points where I discovered 
them they had not been exposed to decomposition in the atmosphere 
ever since their emergence. On the contrary, the adhering shells 
had been protected by a covering of shelly sand only removed of 
late years for road-making. I need scarcely insist upon the obvious 
