36 | Great Geologists
By 1831, Sedgwick had begun field work
in North Wales (he was “burnt as brown
as a pack-saddle, and a little thin from
excessive fatigue” he wrote to a friend),
examining the region’s slaty, largely
unfossiliferous rocks that he understood
to be very old. Murchison placed great
emphasis on fossil content; but, perhaps
due to his mathematical background,
Sedgwick was equally content developing
an understanding of the structure of a
region. This was to prove particularly useful
in determining the stratigraphic position of
much of the North Wales succession.
Adam Sedgwick in 1832, aged 47, from a
painting by Thomas Phillips.
contributed to Wordworth’s “A Complete
Guide to the English Lakes” with a section
entitled “The geology of the Lake District in
four letters addressed to W. Wordsworth,
Esq.”
Sedgwick formed an alliance with one
of the younger fellows of the Geological
Society, Roderick Murchison. From
1827 to around 1840, they were a
prolific partnership that created the basis
for understanding much of Paleozoic
stratigraphy. Unfortunately, it was a
partnership destined to end in acrimony
and a complete severing of their friendship.
Their first field trip, in 1827, visited the
western and northern coasts of Scotland
(mostly by boat and in a fairly superficial
manner), the main aim being to understand
the stratigraphic position of the red
sandstones that formed significant portions
of the outcrop.
In 1834, he undertook what was to prove
a definitive joint field trip with Murchison
to the Welsh Borderlands. The result was
a seminal statement on their Paleozoic
geology: “On the Silurian and Cambrian
Systems, Exhibiting the Order in which the
Older Sedimentary Strata Succeeded Each
Other in England and Wales” (read in 1835
and published in 1836). The term Cambrian
was introduced for Sedgwick’s slates of
North Wales, and Silurian for the younger
fossiliferous rocks upon which Murchison
had focused much of his attention.
Ultimately, the boundary between the two
systems was to prove divisive. Murchison
(see seperate biography) possessed a
vainglorious temperament. Styled by
his admirers the “King of Siluria”, he
sought to expand his Silurian “kingdom”,
ultimately wishing to include rocks
containing the oldest fossils. This included
rocks that Sedgwick was adamant should
be classified as Cambrian. Murchison
persuaded the Geological Survey to colour
much of their map of Wales as Silurian.
This was too much for Sedgwick. He
compared himself to a man who comes
home to find “that a neighbour has turned
out his furniture, taken possession, and
locked the door upon him”. Murchison
had “Silurianized the map of Wales”. The
partnership was broken and the controversy
only resolved by Charles Lapworth after the
death of both Murchison and Sedgwick,
when he introduced the Ordovician System,
placed between Cambrian and Silurian.
Before the schism between Murchison
and Sedgwick, they collaborated on one
important project that led to the creation of
the Devonian system in 1839. Controversy
existed regarding the stratigraphic position
and nature of the “Grauwackes” present
in the county of Devon in south-west
England, that lay beneath Carboniferous
limestones. Murchison’s initial position
was to claim these for his Silurian System,
but paleontological evidence suggested
something more akin to Carboniferous
strata. This dilemma was eventually
resolved through the study of sections
in Europe, especially in the Rhineland
area, which indicated that these rocks
represented a correlative with the Old
Red Sandstone that warranted a separate
stratigraphic term. Accordingly, “Devonian”
was introduced in a joint paper by Sedgwick
and Murchison in 1839.
Sedgwick served as president of the
Geological Society from 1829 to 1831. His
presidency coincided with the publication
of Principals of Geology by Charles Lyell,
a book that did much to both popularise
geology and provide an embracing theory to
explain geological observations.
Sedgwick was not taken with the
uniformitarianism of Lyell. In his heart,
he supported the more catastrophist
views of Baron Georges Cuvier. He
was greatly impressed by the work of
the French geologist Jean-Baptiste Elie
de Beaumont, whose recognition of
angular unconformities in the mountain
ranges of Europe seemed to provide
evidence of sudden cataclysmic events in
geological history. In his 1831 presidential
address, whilst congratulating Lyell on his
magnificent opus, Sedgwick did not hold
back from criticising how, in the style of an
advocate (which indeed Lyell was!), Lyell
had sought observations to support his
theory, rather than vice versa.
Early in his career, Sedgwick was a
“diluvianist”, interpreting widespread
boulder clays as the result of deposition
from the great flood of the bible. By 1831,
Sedgwick had seen enough evidence