C.—GEOLOGY. 55 
might be rising about a pivot, while the German coast remained stationary. 
The facts for both sides of the Baltic were reaffirmed by a joint enquiry 
of the Swedish Academy of Sciences and the Russian Ministry of Marine ; 
but the inferred rise of the land was rejected by Lyell in the first volume 
of his Principles (1830, pp. 231-2). He attributed the recession of the sea 
to the accumulation of sediment and the movement of water in the Baltic 
by the wind ; the beds of shells, 200 ft. above the sea, as at Uddevalla, he 
thought an example of events that are. geologically modern being 
historically ancient. Lyell concluded that ‘the phenomena do not lend 
the slightest support to the Celsian hypothesis, nor to that extraordinary 
notion proposed in our own times by Von Buch, who imagines that the 
whole of the land along the northern and western shores of the Baltic is 
slowly and insensibly rising ! ’ 
Lyell’ fortunately examined the evidence for himself and after a tour 
in Sweden, in a paper read to the Association in 1834, accepted Von 
Buch’s conclusion and the fact that parts of the Baltic coast are rising 
two to three feet in a century, while other parts are stationary. 
The Baltic, therefore, gives convincing testimony of the mobility of 
the land, which is accepted in an extreme form by some champions of 
isostacy. That principle was put forward from the geological evidence 
that the rate of the accumulation of sediments so often coincides with 
the rate of subsidence that the two processes must be dependent, the 
weight of the sediment being the cause of the subsidence. The correlative, 
that the unloading of an area by denudation causes its uplift, was advanced 
by Clarence King (1876). This cause of the rise and fall of land was 
maintained by Airy (1855) and Pratt (1855, 1859, 1871, &c.), when they 
found that the mass of the Himalaya is compensated by a deficiency of 
material in the foundations, and was supported by the gravity surveys 
of the United States by Hayford, and of the oceanic floors by Hecker and 
Duffield. The relief of the earth was attributed to the differences in the 
density of the crust, and the whole surface was regarded as maintained 
in hydrostatic equilibrium, the mountains rising above the general level 
because of the lightness of their foundations, as in the Arctic Sea icebergs 
and hummocks float higher than the floes. 
From this doctrine it is claimed that the subsidence of the crust to 
form oceanic basins, and its uplift into continental masses from oceanic 
depths are both impossible: and that the oceans and continents have 
occupied approximately their present positions throughout the whole of 
geological time. That theory was of service as a reaction against the 
lightly assumed interchange, as pictured by Tennyson, of roaring streets 
and central seas; but the form of isostacy that represents the earth’s 
major relief as determined by the perfect hydrostatic equilibrium of the 
crust is opposed to weighty evidence. 
Geology has constantly suffered from the acceptance of views based 
on mathematical deductions. For a couple of decades during the past 
century geological progress was disturbed by the verdict that the age 
of the earth is somewhere between ten million and a hundred million years. 
8 4th Rep. B.A., pp. 652-4; repeated in his Bakerian Lecture to the Royal 
Society the following year. Phil. Trans., 1835, pp. 1-38. 
