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Dictionary of the History of Ideas

Studies of Selected Pivotal Ideas

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Uniformitarianism assumes the principle that the past
history of the earth is uniform with the present in terms
of the physical laws governing the natural order, the
physical processes occurring both within the earth and
on its surface, and the general scale and intensity of
these processes. It asserts further that our only means
of interpreting the history of the earth is to do so by
analogy with events and processes in the present.

Catastrophism assumes the principle that conditions
on the earth during the past were so different from
those existing in the present that no comparison is
possible, that earthquakes, volcanic eruptions, and the
elevation of mountains and floods occurred during the
past on a scale many times greater than that of any
similar events observable in the modern world, and that
geological events in the past were often so violent and
catastrophic, that they sometimes destroyed all the
species living in particular districts.

The questions raised by the conflicting assumptions
of uniformitarianism and catastrophism apply most
directly to the interpretation of geological history, but
are not restricted to it. These questions arise in science
whenever there is need to interpret natural events
occurring at a distance in space or time. In these
circumstances the separation of the events or processes
from the observing scientist requires him either to
interpret them by analogy with events and processes
closer at hand and more directly observable, or, to
assume that the distant events are the result of proces-
ses unknown to him and are, therefore, impossible to
interpret. If a scientist attempts to interpret distant
events by analogy, he is assuming the uniformity of
the natural order through space and time.


The terms “catastrophism” and “uniformitarianism”
were introduced in 1837 by William Whewell in his
History of the Inductive Sciences to describe the two
leading schools of theoretical geology at that time.
Catastrophism, which was the older theoretical view-
point, was in England widely accepted and defended
by the older generation of geologists, but its leading
exponents were then on the Continent. Leopold von
Buch, the German geologist, had presented a theory
of craters of elevation to account for the form of
volcanic mountains. He supposed that such volcanoes
as Teneriffe in the Canary Islands had not been built
up gradually by many repeated volcanic eruptions
carried on over an immense period of time, but by
an upheaval of the surrounding rock strata, and that
this upheaval had been essentially a single event, cat-
astrophic in nature, and without parallel in the mod-
ern world. Von Buch presented this theory in 1824 after
a visit to the Canary Islands, and in 1829 Léonce Élie
de Beaumont published his theory of the sudden and
simultaneous elevation of mountain chains. He had
been struck by the fact that a number of ranges of
mountains tended to be composed of rocks of similar
geological age and showed similarities of structure. For
instance, de Beaumont suggested that the Pyrenees had
been uplifted in a single sudden upthrow (en un seul
) and that this elevation had occurred at the same
time as that of the Alps. Von Buch and de Beaumont
suggested that in the geological past there had occurred
events on such an enormous scale as to be catastrophic
in nature and without counterpart in the modern expe-
rience of man. Their view of the history of the world
was that while conditions on the earth's surface in
modern times, that is, since the appearance of man
on earth, had been relatively orderly and calm, undis-
turbed by any great changes which might destroy a
significant portion of life on earth, this stable and
reliable condition of the earth's surface was of rela-
tively recent appearance. During the geological past,
they assumed that, while there may have been long
periods of calm conditions, the earth had also been
subjected repeatedly to enormous changes, great shak-
ings of the surface of the whole earth, which had
resulted in the throwing up of mountain ranges, vast
floods, subsidences, and other catastrophes.

In assuming the extraordinary and catastrophic na-
ture of the earth's history, von Buch and de Beaumont
were part of a tradition of geological thinking which
extended back to the seventeenth century and was
deeply influenced by the account of the Creation in
Genesis. Genesis takes for granted that the condition
of the world at the time of its creation was different
from its present state, and this assumption was
accepted unquestioningly by late seventeenth- and
early eighteenth-century writers on the origin of the
world. Even if one leaves aside extravagant and uncrit-
ical writers like Thomas Burnet whose Sacred Theory
of the Earth
(1681-89) was an imaginative but com-
pletely uncritical account of the origin and history of
the earth, the ideas of a cautious and disciplined scien-
tist like John Ray nonetheless take for granted that the
account in Genesis did reflect the actual events which
occurred at the origin of the world and, furthermore,
that the present world was temporary and would dis-
appear in a great conflagration at the day of judgment.
In the early eighteenth century, it became generally
recognized that the fossils found in rocks were the
actual remains of once living animals. For geologists
in Italy fossils demonstrated that the Italian rock strata
had been laid down beneath the sea, because the well
preserved fossil shells in the Italian strata were recog-
nizably similar to the shells species living in the
Mediterranean. For geologists in England and in
northern Europe, however, the recognition of fossils
as the remains of once living animals posed the
difficulty that they belonged to species without
counterparts in the north Atlantic, or in other parts
of the world, for that matter. Thus the fossils of the
English strata suggested the existence of multitudes of
species in the past which had since died out. The
disappearance of such multitudes of species also
suggested that they must have been destroyed by some
great catastrophic event on the earth's surface.

Of the geological theories put forward during the
eighteenth century, perhaps the most influential was
that of Abraham Gottlob Werner. As a professor at
the School of Mines at Frêyburg, Werner became
expert in the recognition of rocks and minerals.

In 1793 Peter Simon Pallas, as a result of his study
of the two principal mountain ranges of Siberia,
decided that the characteristic structure of mountain
ranges was a central core of granite with schistose rocks
containing no fossils along the flanks of the granite,
and with fossil-bearing limestone rocks lying outside
and above the schistose. Pallas' observations on the
structure of mountain ranges, and those of Horace
Bénédict de Saussure on the Alps, appear to have been
used by Werner in the development of his theory of
the earth. Werner assumed that the granite represented
the original surface of the earth formed when the earth
had cooled from a molten mass. He thought that the
schistose rocks had been deposited from the universal
ocean, which, in the first stages of the earth's history,
had covered the whole surface of the earth and had
been as deep as the mountains are high. The schistose
rocks had been chemical precipitates from the


primordial ocean, but at a later stage mechanical sedi-
ments had been deposited from this ocean, giving rise
to the strata of limestone, shale, and sandstone.

Werner's assumption that granite represented the
original surface of the earth and was consequently the
oldest rock, was challenged in 1795 by James Hutton
in his Theory of the Earth with Proofs and Illustrations.
Hutton had been impressed by the fact that the strati-
fied rocks were sediments which, to his mind, must
have been laid down beneath the sea. These sediments,
laid down originally as soft sand, mud, or marl, had
somehow been consolidated into solid rock and had
then been raised from the sea bottom to form dry land
and even hills and mountains. The force which pro-
duced both the consolidation of sediments into rock
and their elevation into hills and mountains was heat.
Hutton was evidently impressed by the discovery of
specific and latent heats by his friend Joseph Black,
the physicist. Hutton considered heat as a force
inherent in matter, moreover, as a repulsive force,
derived ultimately from the sun. It might assume the
form of specific heat; in which case it influenced the
volume of matter, or, latent heat, which determined
the fluidity of matter, or light, or electricity. Heat
which was so diverse in its form and its effects, existed
abundantly within the earth and acted both to consoli-
date sediments into rock and to elevate them. In 1788
Hutton discovered in Glen Tilt in the highlands of
Scotland, a dyke of granite, which had clearly intruded
into the surrounding schistose strata. Not only had the
granite intruded into the stratified rock, but it had
intruded in a molten condition because the strata in
the vicinity of the dyke were much altered, as if by
heat. Hutton was greatly excited by this discovery
because it meant that the granite was not the oldest
rock and did not represent the primordial surface of
the earth. Instead, it represented a later intrusion, and
the oldest rocks discoverable were stratified rocks
which had themselves originated as sediments. How-
ever, these sediments represented the detritus of some
preexisting land. Hutton was aware that the whole
surface of the land was subject to relentless forces of
erosion and was being worn down steadily by rain and
running water. The wearing down of the land was
necessary to create the sediments which were deposited
on the sea bottom. These sediments accumulated over
immense periods of time, were then in turn hardened
into rock by heat, and elevated from the sea to form
hills and mountains. Hutton saw this process of the
wearing down of land, the deposition of sediments and
their re-elevation extending indefinitely into the past
and continuing indefinitely into the future. He saw the
present surface of the earth, not as fixed and unchang
ing, but as intermediate stage in a continuous process.

Hutton's theory reflects the calm inquiring rational
spirit of the eighteenth-century Enlightenment; Hutton
possessed the same temper of mind as David Hume,
the philosopher, or Adam Smith, the economist. His
theory was attacked immediately as being dangerous
to religion, and the force of this criticism was
sharpened by the political consequences of the French
Revolution. In Great Britain the French Revolution
was felt to endanger the whole fabric of social order,
of which the Christian religion was the essential foun-
dation. Hutton's theory left no place for the Mosaic
account of Creation and of the Flood. It assumed that
the earth and the physical order of nature were eternal
and unchanging. At the same time that Hutton's theory
was being attacked on religious and scientific grounds,
liberal political ideas had become unpopular in Britain,
and a repressively reactionary tone dominated politics.
At Edinburgh where Hutton's friends continued to
support his theory after his death in 1797, Robert
Jameson, professor of natural history at the University
of Edinburgh, was one of the most vigorous exponents
of the Wernerian theory. Consequently, the contro-
versy between the Wernerians and Huttonians raged
with a special vigor at Edinburgh between 1800 and
1810. Hutton's friends, several of whom were associ-
ated with the Edinburgh Review, tended to be liberal
in their outlook, whereas the Wernerians were Tories,
and these political associations tended to deepen and
embitter the scientific controversy.

The Wernerian-Huttonian controversy at Edinburgh
did have the effect of convincing geologists of the
dangers of theoretical controversy. Thus, when the
Geological Society of London was founded in 1807,
its members decided to avoid theoretical discussion in
favor of a broad program of geological field studies.
Geological evidence, which could not be interpreted
in terms of the Huttonian theory, was also accumulat-
ing. In 1811 Alexandre Brongniart and Georges Cuvier
published their description of the Tertiary strata of the
Paris basin. Among these strata Cuvier and Brongniart
found a repeated alternation of fresh water and marine
sediments. Such an alternation required either repeated
incursion of the sea over the land, or repeated sub-
sidences and re-elevations of the land. Hutton's
theory provided for neither contingency. At the same
time, Cuvier and Brongniart had described a whole
series of sediments unknown to Werner. In 1812 Cuvier
also published the first edition of his Recherches sur
les ossemens fossiles
(1812-26) based upon his recon-
struction of fossil animals during the preceding fifteen
years. This work presented to the scientific world a
succession of populations of animals, all extinct, and


sometimes both larger in size and more numerous in
species than the animals of modern times. Cuvier
asserted that each successive assemblage of fossil spe-
cies of animals had been destroyed by a geological
catastrophe, such as might occur when the sea rose
to cover the land. He did not hesitate to extend the
consequences of his observations made in the Paris
basin to the whole world. Cuvier was as skillful a
politician as an anatomist, and his theory of successive
catastrophes, the most recent of which was the flood
described in the Bible, appealed strongly to the reli-
gions because it allowed the numerous and striking
recent discoveries in paleontology to be reconciled,
however uncritically, to the biblical account of crea-
tion. After 1815 Cuvier's catastrophism was perhaps
keyed to the intellectual tone of the Bourbon restora-
tion, but it was also popular in the English-speaking
world. An English translation by Robert Kerr was
published at Edinburgh in 1815 and again in many
subsequent editions.

Perhaps paleontology tended to strengthen the
plausibility of catastrophism by the fact that the
discovery of so many large and remarkable fossil ani-
mals suggested that catastrophic events on earth must
have been needed to bring about their disappearance.
In 1812 the skeleton of a remarkable fossil reptile,
seventeen feet long, was found in the blue Lias forma-
tion at Lyme Regis on the coast of Dorsetshire. This
reptile, which had paddle-like appendages to equip it
for swimming, and which in some respects resembled
a fish, in 1816 was named Ichthyosaurus. In 1820 an-
other large swimming reptile, also from the blue Lias,
and with a remarkably long neck was described by
William Daniel Conybeare and was named Plesio-
saurus. This was followed by the discovery of the
enormous Megalosaurus by the Reverend William
Buckland in the Stonefield slate, and of the Iguanodon
by Gideon Mantell in Sussex. In 1825, in the third
edition of his Recherches..., Cuvier described the
Pterodactyls, a group of fossil flying reptiles. These
discoveries all exerted a profound effect on both the
scientific and popular imagination and presented a
vivid picture of the abundance, diversity, and enormous
size and strangeness of past forms of life.

One of the points which had been at issue between
the Huttonians and Wernerians had been the question
of the origin of basalt. Werner had considered that
basalt had been formed by crystallization from water,
whereas Hutton and such French geologists as Jean
Étienne Guettard and Nicholas Desmarest considered
it a volcanic rock. The volcanic origin of basalt was
generally accepted in Britain after 1813 when the
Reverend William Buckland and the Reverend William
Daniel Conybeare visited the Giant's Causeway in
Ireland, where they found clear evidence that that
particularly famous basalt formation had resulted from
a volcanic outflow.

In general, British geologists tended to abandon
Werner's idea that rock strata had been formed by
crystallization or deposition from a universal ocean,
and had accepted the Huttonian idea that the strata
had been laid down beneath the sea and had subse-
quently been elevated. However, in accepting the
concept of movements of the land they necessarily
accepted the occurrence of catastrophes during the
history of the earth, because they could not conceive
how elevations sufficient to create the existing hills and
mountains could occur without catastrophes. In 1814
the English geologist Thomas Webster published a
description of the geology of the Isle of Wight in which
he showed that the chalk strata forming the central
range of hills in the island were vertical or very steeply
inclined and that they formed one side of an anticlinal
fold, the opposite side of which, he discovered on the
south shore of the Isle of Wight. Webster showed that
the strata must once have been continuous in a great
arch extending across the whole Isle of Wight and that
most of this arch had since been removed. The chalk
strata which had formed this arch had been formed
as horizontal beds of sediment in the sea, so that their
upraising to form the arch had required their uplift,
bending, and disturbance on a great scale. This kind
of disturbance was explicable to Webster only by some
enormous convulsion of a kind entirely different from
anything experienced in modern times. The basic as-
sumptions of geologists in the 1820's, whether Hut-
tonian or Wernerian, was stated by William Whewell
in 1831:

In the dislocation of provinces, in the elevation of hills from
the bottom of the sea, in the comminution and dispersion
of vast tracts of the hardest rock, in the obliteration and
renewal of a whole creation they seemed to themselves to
see... the manifestation of powers more energetic and
extensive than those which belonged to the common course
of every day nature.... They spoke of a break in the
continuity of nature's operations; of the present state of
things as permanent and tranquil, the past having been
progressive and violent

(William Whewell, review of Lyell's
Principles of Geology, British Critic, 9 [1831], 190).

During the 1820's the evidence for convulsive and
catastrophic changes in the history of the earth seemed
so compelling and universal that the revival of James
Hutton's concept of a continuous process shaping the
earth's surface indefinitely through time is a develop-
ment requiring some explanation. Two factors seemed
to have played a role. The first may have been an
increasing interest in the study of volcanic activity in
different parts of the world.


Beginning in 1797 Leopold von Buch (1774-1852)
made extensive studies in the Alps where he deter-
mined that their structure showed that they had been
uplifted. From his further observations on the Alban
Hills and Vesuvius in Italy and on Etna in Sicily he
became convinced of the vast extent and power of
volcanic activity, and of its capacity to uplift whole
areas of country. In 1802 he visited the Auvergne
district of France where he found a series of volcanoes
of different ages, all of which were connected with
an underlying platform of granite. He decided that the
mass of trachyte forming the Puy-de-Dôme was simply
granite which had been softened and pushed up as a
protuberance. The other Puys, which possessed the
conical forms and craters characteristic of volcanoes,
had been formed by the ordinary process of volcanic
eruption. After a visit to Norway, where he observed
granite veins extending into an overlying fossil-bearing
limestone which was highly altered along the lines of
contact, von Buch travelled to Madeira and the Canary
Islands. There he saw the results of volcanic activity
on a still larger scale and studied the way in which
the islands had been formed as a result of volcanic
action. He concluded that most oceanic islands were
the products of volcanic activity.

When von Buch studied the form of volcanoes he
noted that they were both conical in form and strati-
fied, with the strata sloping away on all sides from the
crater's summit. He decided that this structure was not
the result of accumulated lava flows, because the lava
emerged in small streams which did not form continu-
ous sheets over the whole surface of the mountain.
When he compared his observations in the Canary
Islands with those he had made in central France, von
Buch decided that each volcano had resulted originally
from a dome-shaped extrusion of molten rock from the
interior of the earth. If this extrusion broke through
to the surface, it solidified while retaining its form and
gave rise to a dome-shaped mountain such as the Puy-
de-Dôme in Auvergne. More often, however, the
extrusion might burst like a bubble at the summit and
collapse inward, thereby forming a cone-shaped vol-
cano of typical form with a crater marking the site
of explosion. In this theory each volcanic mountain was
the product of a single violent eruption instead of the
accumulated product of a long series of eruptions
extended over a great period of time. Von Buch called
the interior molten mass, whose extrusion from the
interior of the earth had given rise to the volcano, a
“Crater of Elevation.” He thought that their extrusion
uplifted the rock strata of the surrounding country in
a catastrophic manner.

On his return to Europe, von Buch again studied
the Alps for a number of years and decided that they
had been formed by a process of upheaval from below,
the upheaving force being volcanic rocks which could
not find their way to the surface because of the thick-
ness of the overlying rock strata.

In 1822 William Daniel Conybeare suggested that
volcanic activity sustained over a long period might
be able to produce a large scale elevation of the land.
Volcanoes were studied by Charles Daubeny, and by
George Poulett Scrope and both studied the area of
extinct volcanoes in the Auvergne district of France
as well as those in Italy and Sicily.

The other factor which may have played a role in
extending the time scale of earth history was the de-
velopment of paleontology, which had also seemed to
support catastrophism by requiring the extinction of
so many successive assemblages of animals and plants.
However, the succession of floras and faunas revealed
by paleontology also required greatly lengthened pe-
riods of time. In addition, the detailed study of the
fossil animals and plants found together in a single bed
frequently suggested the existence of conditions
analogous to those of the present. For instance, in the
Tilgate Forest bed, studied by Gideon Mantell in 1822
and subsequent years, there was a collection of the
bones of turtles, one or more species of crocodiles,
freshwater shells, and the remains of various plants
including tree ferns and large weeds. There were
successive layers of clay and sand, such as might have
been laid down in a modern river delta, and the animals
and plants were comparable to those which might live
in a river delta in a modern tropical country. These
fossils, therefore, suggested that conditions on the
earth's surface at a very remote period of time had
been comparable with those of modern times, although
the climate and latitude of Great Britain had then been
much warmer. In 1824 Charles Lyell gave a reverse
kind of analogy when he compared the plants and
animals living in modern freshwater lakes in Scotland
with the fossil animals and plants found in freshwater
marls of the Paris basin, and found the assemblage of
species very similar in both instances.

From 1820 to 1828 Charles Lyell was first a law
student and later a practicing barrister, but through
the whole time, he was an enthusiastic amateur
geologist and naturalist. He travelled frequently and
extensively. In 1818 he had toured Switzerland and
northern Italy. In 1820 he returned to Switzerland and
this time went as far south in Italy as Rome. He made
frequent excursions on horseback through southern
England, and in 1823 spent many weeks in Paris where
he became acquainted with the Parisian geologists and
studied the geology of the Paris basin. In 1824 he spent
an extended period in Scotland. These travels gave him
a broader experience of landscape, geography, and


geology than many of his contemporaries had. In 1828
Lyell travelled with Roderick Murchison through the
Auvergne district of France, then southward to Nice
and along the coast into Italy. At Padua, Murchison
turned back, but Lyell went on south through Italy
to Naples and made a tour of Sicily. One of his chief
geological discoveries during this journey was that the
Tertiary beds of the Paris basin formed only the earliest
part of the succession of Tertiary formations, and that
in Italy and Sicily there were three series of Tertiary
strata, each successively younger than those of the Paris
basin. Ultimately he named them the Eocene, Miocene,
and older and newer Pliocene formations, of which the
Eocene represented the beds of the Paris basin. Taken
together, the whole series of Tertiary strata were at
least equal in total depth to the succession of secondary
strata in England. In southern Italy and Sicily Lyell
found that the newer Pliocene strata contained fossil
shells, almost entirely belonging to species still living
in the Mediterranean. He also found that these strata
which were close to the active volcanoes of Vesuvius
and Etna appeared to have been uplifted by volcanic
activity. He became convinced that volcanic activity
and earthquakes were both the causes of and manifes-
tations of uplift.

In a letter to Roderick Murchison written as he was
returning northward, Lyell expressed the geological
conviction to which his tour had led him:

That no causes whatever have from the earliest time to
which we can look back, to the present, ever acted but
those now acting and that they never acted with different
degrees of energy from that which they now exert

Letters and Journals of Sir Charles Lyell Bart,
ed. K. M.
Lyell, 2 vols., London [1881], I, 234).

He was stating the central principle of what was to
be known as uniformitarianism. As a principle, it was
the outgrowth of Lyell's geological experience, but it
must be emphasized that it was not, and is not, a
demonstrable scientific conclusion. Instead, it is a
statement of faith and a working hypothesis which is,
nonetheless, a hypothesis indispensable to the progress
of geology as a science. Lyell assumed that gradual
causes acting through long periods of time might exert
large-scale effects. His further assumption, that all
geological effects are the result of gradual causes acting
over large periods, required him to study relentlessly
the existing processes going on both in the earth and
over its surface, to pursue their consequences, and to
estimate their rates. His principle of uniformity re-
quired Lyell always to attempt to explain geological
phenomena and never to abandon this attempt to seek
explanation by dismissing phenomena as the result of
catastrophic events of unknown origin and magnitude.
Lyell assumed that the order of nature and the physical
laws of nature remained constant through time. He
saw, too, that our only possibility of attaining knowl-
edge of the geological past was by analogy with mod-
ern conditions. The geologist had to assume that con-
ditions in the past were comparable to those of the
present and that processes going on in the past were
comparable to processes going on at the present time,
or else he would have to abandon all hope of acquiring
any knowledge of the past.

Furthermore, Lyell's principle of uniformity opened
up to the geologist a multitude of questions for investi-
gation because the whole present order of nature,
existing both over the earth's surface and within its
interior, became relevant to his purpose. Hence, the
geologist must seek to learn what is going on at the
present in order to understand what has gone on in
the past. Catastrophism, on the other hand, removes
the necessity for investigating modern processes be-
cause events in the past are considered to have no
counterparts in the present. The explosion which oc-
curred at the time of emergence of a “Crater of Eleva-
tion” occurred only once and is not to be understood
from the study of modern volcanic activity. The effect
of catastrophic explanations in each instance in which
they were used and in which they are used today, is
to close off further investigation. Lyell stressed that
an enlarged view of the existing order of nature was
the primary requisite for a geologist, and the chief
means of attaining this enlarged view was travel. He

To travel is of first, second, and third importance to those
who desire to originate just and comprehensive views con-
cerning the structure of our globe

(Lyell, Principles of
11th ed., 2 vols., London [1872], 1, 69).

During his lifetime Lyell upheld the principle of
uniformity in eleven successive editions of his Principles
of Geology,
published between 1830 and 1872, and in
other books and memoirs. With unequalled insight, he
interpreted a vast range of geological data in terms
of processes observable in the modern world. Of even
more far-reaching significance was his influence on
Charles Darwin. During the voyage of the H. M. S.
Beagle, 1831-36, Darwin came to appreciate the great
value of the approach to geology embodied in Lyell's
Principles. He then applied the same principles to the
interpretation of the geological history of species and
considered what would be the effect of a modern
process, namely, natural selection, if it had continued
to act through an indefinite period of past time.
Darwin's theory of the origin of species by natural


selection may be considered an application of Lyell's
principles of uniformity to the living world.

Towards the end of Lyell's life uniformitarianism was
attacked by the physicist, Lord Kelvin, who in 1865
argued that if the earth had been formed originally
as a hot molten body which had later cooled but which
also continued to lose heat by radiation, its age could
be calculated by extrapolating backward from its pres-
ent rate of heat loss. Kelvin assumed that there was
no source of heat within the earth, other than that
which was present there when the earth was formed.
On his assumptions he showed that the age of the earth
could not be greater than 100,000,000 years and was
probably much less. This short and restricted time span
for the age of the earth would not allow sufficient time
for the extremely slow gradual geological processes,
as viewed by Lyell, to bring about the actual geological
changes which had occurred. The history of the earth
if thus compressed in time would necessarily become
violent and catastrophic. This concept of the earth's
severely limited age would not allow time, either, for
the slow process of evolution of living species by natu-
ral selection, as viewed by Charles Darwin.

In the face of Kelvin's calculations, geologists tended
to retreat from their advocacy of uniformitarianism
after Lyell's death in 1875. In 1897 Sir Archibald
Geikie wrote that uniformitarianism “in its extreme
form is probably held by few geologists in any coun-
try.” By “its extreme form” Geikie meant chiefly a
uniformitarianism which would rule out events on a
catastrophic level in volcanic activity and mountain
building during the geological past. However, with the
discovery of radioactivity, it was pointed out by Ernest
Rutherford in 1904 that the radioactive elements did
provide a steady source of heat within the earth. The
assumptions on which Kelvin had based his estimates
of the age of the earth were, therefore, invalid and
his calculations meaningless. Geologists did not, how-
ever, recover immediately their confidence in uni-
formitarianism, and in many instances they continued
to believe that volcanic activity and mountain building
had gone on during particular periods of the geological
past on a scale, and with an intensity, unparalleled in
the present. In recent years, however, radioactive
methods of dating rocks have shown that instances of
supposed catastrophic volcanic activity and mountain
building have, in fact, occurred over long periods of
geological time. There is, therefore, little reason to
believe that they ever involved systematic volcanic
eruptions or earthquakes of magnitude greater than
those which occur on earth today. The principle of
uniformitarianism may be considered vindicated by
modern science.


Frank Dawson Adams, The Birth and Development of the
Geological Sciences
(Montreal, 1938). Loren Eiseley,
Darwin's Century (New York, 1958). Archibald Geikie, The
Founders of Geology
(London, 1897). Patsy A. Gerstner,
“James Hutton's Theory of the Earth and His Theory of
Matter,” Isis, 59 (1968), 26-31. Charles C. Gillispie, Genesis
and Geology
(Cambridge, Mass., 1951). Leonard G. Wilson,
“The Origins of Charles Lyell's Uniformitarianism,” Uni-
formity and Simplicity,
ed. Claude Albritton, Geological
Society of America, Special Paper 89 (New York, 1967),


[See also Continuity and Discontinuity; Evolutionism;Re-
ligion and Science; Uniformitarianism in Linguistics.]