Encyclopaedia Britannica, 11th Edition, "Destructors" to "Diameter"

Chapter IV: Part 4

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The fossil evidence clearly shows the close agreement of the Rhenish
and south Devonshire areas. In north Devonshire the Devonian rocks
pass upward without break into the Culm.

_North America._--In North America the Devonian rocks are extensively
developed; they have been studied most closely in the New York region,
where they are classified according to Table IV.

The classification below is not capable of application over the states
generally and further details are required from many of the regions
where Devonian rocks have been recognized, but everywhere the broad
threefold division seems to obtain. In Maryland the following
arrangement has been adopted--(1) Helderberg = Coeymans; (2) Oriskany;
(3) Romney = Erian; (4) Jennings = Genesee and Portage; (5) Hampshire
= Catskill in part. In the interior the Helderbergian is missing and
the system commences with (1) Oriskany, (2) Onondaga, (3) Hamilton,
(4) Portage (and Genesee), (5) Chemung.

The Helderbergian series is mainly confined to the eastern part of the
continent; there is a northern development in Maine, and in Canada
(Gaspé, New Brunswick, Nova Scotia and Montreal); an Appalachian belt,
and a lower Mississippian region. The series as a whole is mainly
calcareous (2000 ft. in Gaspé), and thins out towards the west. The
fauna has Hercynian affinities. The Oriskany formation consists
largely of coarse sandstones; it is thin in New York, but in Maryland
and Virginia it is several hundred feet thick. It is more widespread
than the underlying Helderbergian. The Lower Devonian appears to be
thick in northern Maine and in Gaspé, New Brunswick and Nova Scotia,
but neither the palaeontology nor the stratigraphy has been completely
worked out.

In the Middle Devonian the thin clastic deposits at the base, Esopus
and Schoharie grits, have not been differentiated west of the
Appalachian region; but the Onondaga limestones are much more
extensive. The Erian series is often described as the Hamilton series
outside the New York district, where the _Marcellus_ shales are
grouped together with the Hamilton shales, and numerous local
subdivisions are included, as in Ohio, Kentucky and Tennessee. The
rocks are mostly shales or slates, but limestones predominate in the
western development. In Pennsylvania the Hamilton series is from 1500
ft. to 5000 ft. thick, but in the more calcareous western extension it
is much thinner. The _Marcellus_ shales are bituminous in places.

The Senecan series is composed of shallow-water deposits; the Tully
limestone, a local bed in New York, thins out in places into a layer
of pyrites which contains a remarkable dwarfed fauna. The bituminous
Genesee shales are thickest in Pennsylvania (300 ft.); 25 ft. on Lake
Erie. The shales and sandstones of the Portage formation reach 1000
ft. to 1400 ft. in western New York. In the Chautauquan series the
Chemung formation is not always clearly separable from the Portage
beds, it is a sandstone and conglomerate formation which reaches its
maximum thickness (8000 ft.) in Pennsylvania, but thins rapidly
towards the west. In the Catskill region the Upper Devonian has an Old
Red facies--red shales and sandstones with a freshwater and brackish
fauna.

TABLE IV.

+---------------+-------------------------------+-------------+
| | | Probable |
| Groups. | Formations. | European |
| | | Equivalent. |
+---------------+-------------------------------+-------------+
/ | Chautauquan. | Chemung beds with Catskill | Famennien. |
U | | | as a local facies. | |
P | | | | |
P < | ( | Portage beds (Naples, Ithaca | Frasnien. |
E | | ( | and Oneonta shales as local | |
R | | Senecan. < | facies). | |
. | | ( | Genesee shales. | |
\ | ( | Tully limestone. | |
+---------------+-------------------------------+-------------+
M / | Erian. ( | Hamilton shale. | Givétien. |
I | | ( | Marcellus shale. | |
D | | | | |
D < | ( | Onondaga (Corniferous) | Eifélien. |
L | | Ulsterian. ( | limestone. | |
E | | < | Schoharie grit. | |
. \ | ( | Esopus grit (Caudagalli grit).| |
+---------------+-------------------------------+-------------+
L / | Oriskanian. | Oriskany sandstone. | Coblentzien.|
O | | | | |
W | | ( | Kingston beds. | Gédinnien. |
E < |Helderbe- ( | Becraft limestone. | |
R | | rgian. < | New Scotland beds. | |
. | | ( | Coeymans limestone. | |
\ +---------------+-------------------------------+-------------+

Although the correlation of the strata has only advanced a short
distance, there is no doubt as to the presence of undifferentiated
Devonian rocks in many parts of the continent. In the Great Plains
this system appears to be absent, but it is represented in Colorado,
Utah, Nevada, Wyoming, Montana, California and Arizona; Devonian rocks
occur between the Sierras and the Rocky Mountains, in the Arbuckle
Mountains of Oklahoma and in Texas. In the western interior limestones
predominate; 6000 ft. of limestone are found at Eureka, Nevada,
beneath 2000 ft. of shale. On the Pacific coast metamorphism of the
rocks is common, and lava-flows and tuffs occur in them.

In Canada, besides the occurrences previously mentioned in the eastern
region, Devonian strata are found in considerable force along the
course of the Mackenzie river and the Canadian Rockies, whence they
stretch out into Alaska. It is probable, however, that much that is
now classed as Devonian in Canada will prove on fossil evidence to be
Carboniferous.

_South America, Africa, Australia, &c._--In South America the Devonian
is well developed; in Argentina, Bolivia, Brazil, Peru and the
Falkland Islands, the palaeontological horizon is about the junction
of the Lower and Middle divisions, and the fauna has affinities with
the Hamilton shales of North America. Nearly allied to the South
American Devonian is that of South Africa, where they are represented
by the Bokkeveld beds in the Cape system. In Australia we find Lower
Devonian consisting of coarse littoral deposits with volcanic rocks;
and a Middle division with coral limestones in Victoria, New South
Wales and Queensland; an Upper division has also been observed. In New
Zealand the Devonian is well exposed in the Reefton mining field; and
it has been suggested that much of the highly metamorphosed rock may
belong to this system.

_Stratigraphy of the Old Red Sandstone Facies._

The Old Red Sandstone of Britain, according to Sir Archibald Geikie,
"consists of two subdivisions, the lower of which passes down
conformably into the Upper Silurian deposits, the upper shading off
in the same manner into the base of the Carboniferous system, while
they are separated from each other by an unconformability." The Old
Red strata appear to have been deposited in a number of elongated
lakes or lagoons, approximately parallel to one another, with a
general alignment in a N.E.-S.W. direction. To these areas of deposit
Sir A. Geikie has assigned convenient distinctive names.

In Scotland the two divisions of the system are sharply separated by a
pronounced unconformability which is probably indicative of a
prolonged interval of erosion. In the central valley between the base
of the Highlands and the southern uplands lay "Lake Caledonia." Here
the lower division is made up of some 20,000 ft. of shallow-water
deposits, reddish-brown, yellow and grey sandstones and conglomerates,
with occasional "cornstones," and thin limestones. The grey flagstones
with shales are almost confined to Forfarshire, and are known as the
"Arbroath flags." Interbedded volcanic rocks, andesites, dacites,
diabases, with agglomerates and tuffs constitute an important feature,
and attain a thickness of 6000 ft. in the Pentland and Ochil hills. A
line of old volcanic vents may be traced in a direction roughly
parallel to the trend of the great central valley. On the northern
side of the Highlands was "Lake Orcadie," presumably much larger than
the foregoing lake, though its boundaries are not determinable. It lay
over Moray Firth and the east of Ross and Sutherland, and extended
from Caithness to the Orkney Islands and S. Shetlands. It may even
have stretched across to Norway, where similar rocks are found in
Sognefjord and Dalsfjord, and may have had communications with some
parts of northern Russia. Very characteristic of this area are the
Caithness flags, dark grey and bituminous, which, with the red
sandstones and conglomerates at their base, probably attain a
thickness of 16,000 ft. The somewhat peculiar fauna of this series led
Murchison to class the flags as Middle Devonian. In the Shetland
Islands contemporaneous volcanic rocks have been observed. Over the
west of Argyllshire lay "Lake Lorne"; here the volcanic rocks
predominate, they are intercalated with shallow-water deposits. A
similar set of rocks occupy the Cheviot district.

The upper division of the Old Red Sandstone is represented in
Shropshire and South Wales by a great series of red rocks, shales,
sandstones and marls, some 10,000 ft. thick. They contain few fossils,
and no break has yet been found in the series. In Scotland this series
was deposited in basins which correspond only partially with those of
the earlier period. They are well developed in central Scotland over
the lowlands bordering the Moray Firth. Interbedded lavas and tuffs
are found in the island of Hoy. An interesting feature of this series
is the occurrence of great crowds of fossil fishes in some localities,
notably at Dura Den in Fife. In the north of England this series rests
unconformably upon the Lower Old Red and the Silurian.

Flanking the Silurian high ground of Cumberland and Westmorland, and
also in the Lammermuir hills and in Flint and Anglesey, a brecciated
conglomerate, presenting many of the characters of a glacial deposit
in places, has often been classed with the Old Red Sandstone, but in
parts, at least, it is more likely to belong to the base of the
Carboniferous system. In Ireland the lower division appears to be
represented by the Dingle beds and Glengariff grits, while the Kerry
rocks and the Kiltorcan beds of Cork are the equivalents of the upper
division. Rocks of Old Red type, both lower and upper, are found in
Spitzbergen and in Bear Island. In New Brunswick and Nova Scotia the
Old Red facies is extensively developed. The Gaspé sandstones have
been estimated at 7036 ft. thick. In parts of western Russia Old Red
Sandstone fossils are found in beds intercalated with others
containing marine fauna of the Devonian facies.

_Devonian and Old Red Sandstone Faunas._

The two types of sediment formed during this period--the _marine_
Devonian and the _lagoonal_ Old Red Sandstone--representing as they do
two different but essentially contemporaneous phases of physical
condition, are occupied by two strikingly dissimilar faunas. Doubtless
at all times there were regions of the earth that were marked off no
less clearly from the normal marine conditions of which we have
records; but this period is the earliest in which these variations of
environment are made obvious. In some respects the faunal break
between the older Silurian below and the younger Carboniferous above
is not strongly marked; and in certain areas a very close relationship
can be shown to exist between the older Devonian and the former, and
the younger Devonian and the latter. Nevertheless, taken as a whole,
the life of this period bears a distinct stamp of individuality.

The two most prominent features of the Devonian seas are presented by
corals and brachiopods. The corals were abundant individually and
varied in form; and they are so distinctive of the period that no
Devonian species has yet been found either in the Silurian or in the
Carboniferous. They built reefs, as in the present day, and
contributed to the formation of limestone masses in Devonshire, on the
continent of Europe and in North America. Rugose and tabulate forms
prevailed; among the former the cyathophyllids (_Cyathophyllum_) were
important, _Phillipsastraea_, _Zaphrentis_, _Acervularia_ and the
curious _Calceola_ (_sandalina_), an operculate genus which has given
palaeontologists much trouble in its diagnosis, for it has been
regarded as a pelecypod (hippurite) and a brachiopod. The tabulate
corals were represented by _Favosites_, _Michelinia_, _Pleurodictyum_,
_Fistulipora_, _Pachypora_ and others. _Heliolites_ and _Plasmopora_
represent the alcyonarians. Stromatoporoids were important reef
builders. A well-known fossil is _Receptaculites_, a genus to which it
has been difficult to assign a definite place; it has been thought to
be a sponge, it may be a calcareous alga, or a curious representative
of the foraminifera.

In the Devonian period the brachiopods reached the climax of their
development: they compose three-quarters of the known fauna, and more
than 1100 species have been described. Changes were taking place from
the beginning of the period in the relative importance of genera;
several Silurian forms dropped out, and new types were coming in. A
noticeable feature was the development of broad-winged shells in the
genus _Spirifer_, other spiriferids were _Ambocoelia_, _Uncites_,
_Verneuilia_. Orthids and pentamerids were waning in importance, while
the productids (_Productella_, _Chonetes_, _Strophalosia_) were
increasing. The strophomenids were still flourishing, represented by
the genera _Leptaena_, _Stropheodonta_, _Kayserella_, and others. The
ancient _Lingula_, along with _Crania_ and _Orbiculoidea_, occur among
the inarticulate forms. Another long-lived and wide-ranging species is
_Atrypa reticularis_. The athyrids were very numerous (_Athyris_,
_Retzia_, _Merista_, _Meristella_, _Kayserina_, &c.); and the
rhynchonellids were well represented by _Pugnax_, _Hypothyris_, and
several other genera. The important group of terebratulids appears in
this system; amongst them _Stringocephalus_ is an eminently
characteristic Devonian brachiopod; others are _Dielasma_,
_Cryptonella_, _Rensselaeria_ and _Oriskania_.

The pelecypod molluscs were represented by _Pterinea_, abundant in the
lower members along with other large-winged forms, and by
_Cucullella_, _Buchiola_ and _Curtonotus_ in the upper members of the
system. Other genera are _Actinodesma_, _Cardiola_, _Nucula_,
_Megalodon_, _Aviculopecten_, &c. Gasteropods were becoming more
important, but the simple capulid forms prevailed: _Platyceras_
(_Capulus_), _Straparollus_, _Pleurotomaria_, _Murchisonia_,
_Macrocheilina_, _Euomphalus_. Among the pteropods, _Tentaculites_ was
very abundant in some quarters; others were _Conularia_ and
_Styliolina_. In the Devonian period the cephalopods began to make a
distinct advance in numbers, and in development. The goniatites appear
with the genera _Anarcestes_, _Agoniatites_, _Tornoceras_, _Bactrites_
and others; and in the upper strata the clymenoids, forerunners of the
later ammonoids, began to take definite shape. While several new
nautiloids (_Homaloceras_, _Ryticeras_, &c.) made their appearance
several of the older genera still lived on (_Orthoceras_,
_Poterioceras_, _Actinoceras_).

Crinoids were very abundant in some parts of the Devonian sea, though
they were relatively scarce in others; they include the genera
_Melocrinus_, _Haplocrinus_, _Cupressocrinus_, _Calceocrinus_ and
_Eleuthrocrinus_. The cystideans were falling off (_Proteocystis_,
_Tiaracrinus_), but blastoids were in the ascendant (_Nucleocrinus_,
_Codaster_, &c.). Both brittle-stars, _Ophiura_, _Palaeophiura_,
_Eugaster_, and true starfishes, _Palaeaster_, _Aspidosoma_, were
present, as well as urchins (_Lepidocentrus_).

When we turn to the crustaceans we have to deal with two distinct
assemblages, one purely marine, trilobitic, the other mainly
lacustrine or lagoonal with a eurypteridian facies. The trilobites had
already begun to decline in importance, and as happens not
infrequently with degenerating races of beasts and men, they began to
develop strange eccentricities of ornamentation in some of their
genera. A number of Silurian genera lived on into the Devonian period,
and some gradually developed into new and distinctive forms; such were
_Proëtus_, _Harpes_, _Cheirurus_, _Bronteus_ and others. Distinct
species of _Phacops_ mark the Lower and Upper Devonian respectively,
while the genus _Dalmania_ (_Odontochile_) was represented by species
with an almost world-wide range. The Ostracod _Entomis_ (_Cypridina_)
was extremely abundant in places--_Cypridinen-Schiefer_--while the
true _Cypridina_ was also present along with _Beyrichia_,
_Leperditia_, &c. The Phyllocarids, _Echinocaris_, _Eleuthrocaris_,
_Tropidocaris_, are common in the United States. It is in the Old Red
Sandstone that the eurypterids are best preserved; foremost among
these was _Pterygotus_; _P. anglicus_ has been found in Scotland with
a length of nearly 6 ft.; _Eurypterus_, _Slimonia_, _Stylonurus_ were
other genera.

Insects appear well developed, including both orthopterous and
neuropterous forms, in the New Brunswick rocks. Mr Scudder believed he
had obtained a specimen of Orthoptera in which a stridulating organ
was present. A species of _Ephemera_, allied to the modern may-fly,
had a spread of wing extending to 5 in. In the Scottish Old Red
Sandstone myriapods, _Kampecaris_ and _Archidesmus_, have been
described; they are somewhat simpler than more recent forms, each
segment being separate, and supplied with only one pair of walking
legs. Spiders and scorpions also lived upon the land.

The great number of fish remains in the Devonian and Old Red strata,
coupled with the truly remarkable characters possessed by some of the
forms, has caused the period to be described as the "age of fishes."
As in the case of the crustaceans, referred to above, we find one
assemblage more or less peculiar to the freshwater or brackish
conditions of the Old Red, and another characteristic of the marine
Devonian; on the whole the former is the richer in variety, but there
seems little doubt that quite a number of genera were capable of
living in either environment, whatever may have been the real
condition of the Old Red waters. Foremost in interest are the curious
ostracoderms, a remarkable group of creatures possessing many of the
characteristics of fishes, but more probably belonging to a distinct
class of organisms, which appears to link the vertebrates with the
arthropods. They had come into existence late in Silurian times; but
it is in the Old Red strata that their remains are most fully
preserved. They were abundant in the fresh or brackish waters of
Scotland, England, Wales, Russia and Canada, and are represented by
such forms as _Pteraspis_, _Cephalaspis_, _Cyathaspis_, _Tremataspis_,
_Bothriolepis_ and _Pterichthys_.

In the lower members of the Old Red series _Dipterus_, and in the
upper members _Phaneropleuron_, represented the dipnoid lung-fishes;
and it is of extreme interest to note that a few of these curious
forms still survive in the African _Protopterus_, the Australian
_Ceratodus_ and the South American _Lepidosiren_,--all freshwater
fishes. Distantly related to the lung-fishes were the singular
arthrodirans, a group possessing the unusual faculty of moving the
head in a vertical plane. These comprise the wide-ranging _Coccosteus_
with _Homosteus_ and _Dinichthys_, the largest fish of the period. The
latter probably reached 20 ft. in length; it was armed with
exceedingly powerful jaws provided with turtle-like beaks. Sharks were
fairly prominent denizens of the sea; some were armed with cutting
teeth, others with crushing dental plates; and although they were on
the whole marine fishes, they were evidently able to live in fresher
waters, like some of their modern representatives, for their remains,
mostly teeth and large dermal spines, are found both in the Devonian
and Old Red rocks. _Mesacanthus_, _Diplacanthus_, _Climatius_,
_Cheiracanthus_ are characteristic genera. The crossopterygians,
ganoids with a scaly lobe in the centre of the fins, were represented
by _Holoptychius_ and _Glyptopomus_ in the Upper Old Red, and by such
genera as _Diplopterus_, _Osteolepis_, _Gyroptychius_ in the lower
division. The _Polypterus_ of the Nile and _Calamoichthys_ of South
Africa are the modern exemplars of this group. _Cheirolepis_, found in
the Old Red of Scotland and Canada, is the only Devonian
representative of the actinopterygian fishes. The cyclostome fishes
have, so far, been discovered only in Scotland, in the tiny
_Palaeospondylus_. Amphibian remains have been found in the Devonian
of Belgium; and footprints supposed to belong to a creature of the
same class (_Thinopus antiquus_) have been described by Professor
Marsh from the Chemung formation of Pennsylvania.

_Plant Life._--In the lacustrine deposits of the Old Red Sandstone we
find the earliest well-defined assemblage of terrestrial plants. In
some regions so abundant are the vegetable remains that in places they
form thin seams of veritable coal. These plants evidently flourished
around the shores of the lakes and lagoons in which their remains were
buried along with the other forms of life. Lycopods and ferns were the
predominant types; and it is important to notice that both groups were
already highly developed. The ferns include the genera _Sphenopteris_,
_Megalopteris_, _Archaeopteris_, _Neuropteris_. Among the Lycopods are
_Lycopodites_, _Psilophyton_, _Lepidodendron_. Modern horsetails are
represented by _Calamocladus_, _Asterocalamites_, _Annularia_. Of
great interest are the genera _Cordaites_, _Araucarioxylon_, &c.,
which were synthetic types, uniting in some degree the Coniferae and
the Cycadofilicales. With the exception of obscure markings, aquatic
plants are not so well represented as might have been expected;
_Parka_, a common fossil, has been regarded as a water plant with a
creeping stem and two kinds of sporangia in sessile sporocarps.

_Physical Conditions, &c._--Perhaps the most striking fact that is brought out by a study of the Devonian rocks and their fossils is the gradual transgression of the sea over the land, which took place quietly in every quarter of the globe shortly after the beginning of the period. While in most places the Lower Devonian sediments succeed the Silurian formations in a perfectly conformable manner, the Middle and Upper divisions, on account of this encroachment of the sea, rest unconformably upon the older rocks, the Lower division being unrepresented. This is true over the greater part of South America, so far as our limited knowledge goes, in much of the western side of North America, in western Russia, in Thuringia and other parts of central Europe. Of the distribution of land and sea and the position of the coast lines in Devonian times we can state nothing with precision. The known deposits all point to shallow waters of epicontinental seas; no abyssal formations have been recognized. E. Kayser has pointed out the probability of a Eurasian sea province extending through Europe towards the east, across north and central Asia towards Manitoba in Canada, and an American sea province embracing the United States, South America and South Africa. At the same time there existed a great North Atlantic land area caused partly by the uplift of the Caledonian range just before the beginning of the period, which stretched across north Europe to eastern Canada; on the fringe of this land the Old Red Sandstone was formed.

In the European area C. Barrois has indicated the existence of three zones of deposition: (1) A northern, Old Red, region, including Great Britain, Scandinavia, European Russia and Spitzbergen; here the land was close at hand; great brackish lagoons prevailed, which communicated more or less directly with the open sea. In European Russia, during its general advance, the sea occasionally gained access to wide areas, only to be driven off again, during pauses in the relative subsidence of the land, when the continued terrigenous sedimentation once more established the lagoonal conditions. These alternating phases were frequently repeated. (2) A middle region, covering Devonshire and Cornwall, the Ardennes, the northern part of the lower Rhenish mountains, and the upper Harz to the Polish Mittelgebirge; here we find evidence of a shallow sea, clastic deposits and a sublittoral fauna. (3) A southern region reaching from Brittany to the south of the Rhenish mountains, lower Harz, Thuringia and Bohemia; here was a deeper sea with a more pelagic fauna. It must be borne in mind that the above-mentioned regions are intended to refer to the time when the extension of the Devonian sea was near its maximum. In the case of North America it has been shown that in early and middle Devonian time more or less distinct faunas invaded the continent from five different centres, viz. the Helderberg, the Oriskany, the Onondaga, the southern Hamilton and the north-western Hamilton; these reached the interior approximately in the order given.

Towards the close of the period, when the various local faunas had mingled one with another and a more generalized life assemblage had been evolved, we find many forms with a very wide range, indicating great uniformity of conditions. Thus we find identical species of brachiopods inhabiting the Devonian seas of England, France, Belgium, Germany, Russia, southern Asia and China; such are, _Hypothyris_ (_Rhynchonella_) _cuboides_, _Spirifer disjunctus_ and others. The fauna of the _Calceola_ shales can be traced from western Europe to Armenia and Siberia; the _Stringocephalus_ limestones are represented in Belgium, England, the Urals and Canada; and the (_Gephyroceras_) _intumescens_ shales are found in western Europe and in Manitoba.

The Devonian period was one of comparative quietude; no violent crustal movements seem to have taken place, and while some changes of level occurred towards its close in Great Britain, Bohemia and Russia, generally the passage from Devonian to Carboniferous conditions was quite gradual. In later periods these rocks have suffered considerable movement and metamorphism, as in the Harz, Devonshire and Cornwall, and in the Belgian coalfields, where they have frequently been thrust over the younger Carboniferous rocks. Volcanic activity was fairly widespread, particularly during the middle portion of the period. In the Old Red rocks of Scotland there is a great thickness (6000 ft.) of igneous rocks, including diabases and andesitic lavas with agglomerates and tuffs. In Devonshire diabases and tuffs are found in the middle division. In west central Europe volcanic rocks are found at many horizons, the most common rocks are diabases and diabase tuffs, _schalstein_. Felsitic lavas and tuffs occur in the Middle Devonian of Australia. Contemporaneous igneous rocks are generally absent in the American Devonian, but in Nova Scotia and New Brunswick there appear to be some.

There is little evidence as to the climate of this period, but it is interesting to observe that local glacial conditions _may_ have existed in places, as is suggested by the coarse conglomerate with striated boulders in the upper Old Red of Scotland. On the other hand, the prevalence of reef-building corals points to moderately warm temperatures in the Middle Devonian seas.

The economic products of Devonian rocks are of some importance: in many of the metamorphosed regions veins of tin, lead, copper, iron are exploited, as in Cornwall, Devon, the Harz; in New Zealand, gold veins occur. Anthracite of Devonian age is found in China and a little coal in Germany, while the Upper Devonian is the chief source of oil and gas of western Pennsylvania and south-western New York. In Ontario the middle division is oil-bearing. Black phosphates are worked in central Tennessee, and in England the marls of the "Old Red" are employed for brick-making.

REFERENCES.--The literature of the Devonian rocks and fossils is very
extensive; important papers have been contributed by the following
geologists: J. Barrande, C. Barrois, F. Béclard, E. W. Benecke, L.
Beushausen, A. Champernowne, J. M. Clarke, Sir J. W. Dawson, A.
Denckmann, J. S. Diller, E. Dupont, F. Frech, J. Fournet, Sir A.
Geikie, G. Gürich, R. Hoernes, E. Kayser, C. and M. Koch, A. von
Koenen, Hugh Miller, D. P. Oehlert, C. S. Prosser, P. de Rouville, C.
Schuchert, T. Tschernyschew, E. O. Ulrich, W. A. E. Ussher, P. N.
Wenjukoff, G. F. Whidborne, J. F. Whiteaves and H. S. Williams.
Sedgwick and Murchison's original description appeared in the _Trans.
Geol. Soc._ (2nd series, vol. v., 1839). Good general accounts will be
found in Sir A. Geikie's _Text-Book of Geology_ (vol. ii., 4th ed.,
1903), in E. Kayser's _Lehrbuch der Geologie_ (vol. ii., 2nd ed.,
1902), and, for North America, in Chamberlin and Salisbury's _Geology_
(vol. ii., 1906). See the _Index to the Geological Magazine_
(1864-1903), and in subsequent annual volumes; _Geological Literature
added to the Geological Society's Library_ (London), annually since
1893; and the _Neues Jahrbuch für Min., Geologie und Paläontologie_
(Stuttgart, 2 annual volumes). The U.S. Geological Survey publishes at
intervals a _Bibliography and Index of North American Geology, &c._,
and this (e.g. Bulletin 301,--the _Bibliog. and Index_ for 1901-1905)
contains numerous references for the Devonian system in North America.
(J. A. H.)

DEVONPORT, a municipal, county and parliamentary borough of Devonshire, England, contiguous to East Stonehouse and Plymouth, the seat of one of the royal dockyards, and an important naval and military station. Pop. (1901) 70,437. It is situated immediately above the N.W. angle of Plymouth Sound, occupying a triangular peninsula formed by Stonehouse Pool on the E. and the Hamoaze on the W. It is served by the Great Western and the London & South Western railways. The town proper was formerly enclosed by a line of ramparts and a ditch excavated out of the limestone, but these are in great part demolished. Adjoining Devonport are East Stonehouse (an urban district, pop. 15,111), Stoke and Morice Town, the two last being suburbs of Devonport. The town hall, erected in 1821-1822 partly after the design of the Parthenon, is distinguished by a Doric portico; while near it are the public library, in Egyptian style, and a conspicuous Doric column built of Devonshire granite. This monument, which is 100 ft. high, was raised in commemoration of the naming of the town in 1824. Other institutions are the Naval Engineering College, Keyham (1880); the municipal technical schools, opened in 1899, the majority of the students being connected with the dockyard; the naval barracks, Keyham (1885); the Raglan barracks and the naval and military hospitals. On Mount Wise, which was formerly defended by a battery (now a naval signalling station), stands the military residence, or Government House, occupied by the commander of the Plymouth Coast Defences; and near at hand is the principal naval residence, the naval commander-in-chief's house. The prospect from Mount Wise over the Hamoaze to Mount Edgecumbe on the opposite shore is one of the finest in the south of England. The most noteworthy feature of Devonport, however, is the royal dockyard, originally established by William III. in 1689 and until 1824 known as Plymouth Dock. It is situated within the old town boundary and contains four docks. To this in 1853 was added Keyham steamyard, situated higher up the Hamoaze beyond the old boundary and connected with the Devonport yard by a tunnel. In 1896 further extensions were begun at the Keyham yard, which became known as Devonport North yard. Before these were begun the yard comprised two basins, the northern one being 9 acres and the southern 7 acres in area, and three docks, having floor-lengths of 295, 347 and 413 ft., together with iron and brass foundries, machinery shops, engineer students' shop, &c. The new extensions, opened by the Prince of Wales on the 21st of February 1907, cover a total area of 118 acres lying to the northward in front of the Naval Barracks, and involved the reclamation of 77 acres of mudflats lying below high-water mark. The scheme presented three leading features--a tidal basin, a group of three graving docks with entrance lock, and a large enclosed basin with a coaling depôt at the north end. The tidal basin, close to the old Keyham north basin, is 740 ft. long with a mean width of 590 ft., and has an area of 10 acres, the depth being 32 ft. at low water of spring tides. It affords access to two graving docks, one with a floor-length of 745 ft. and 20½ ft. of water over the sill, and the other with a length of 741 ft. and 32 ft. of water over the sill. Each of these can be subdivided by means of an intermediate caisson, and (when unoccupied) may serve as an entrance to the closed basin. The lock which leads from the tidal to the closed basin is 730 ft. long, and if necessary can be used as a dock. The closed basin, out of which opens a third graving dock, 660 ft. long, measures 1550 ft. by 1000 ft. and has an area of 35½ acres, with a depth of 32 ft. at low-water springs; it has a direct entrance from the Hamoaze, closed by a caisson. The foundations of the walls are carried down to the rock, which in some places lies covered with mud 100 ft. or more below coping level. Compressed air is used to work the sliding caissons which close the entrances of the docks and closed basin. A ropery at Devonport produces half the hempen ropes used in the navy.

By the Reform Act of 1832 Devonport was erected into a parliamentary borough including East Stonehouse and returning two members. The ground on which it stands is for the most part the property of the St Aubyn family (Barons St Levan), whose steward holds a court leet and a court baron annually. The town is governed by a mayor, sixteen aldermen and forty-eight councillors. Area, 3044 acres.

DEVONPORT, EAST and WEST, a town of Devon county, Tasmania, situated on both sides of the mouth of the river Mersey, 193 m. by rail N.W. of Hobart. Pop. (1901), East Devonport, 673, West Devonport, 2101. There is regular communication from this port to Melbourne and Sydney, and it ranks as the third port in Tasmania. A celebrated regatta is held on the Mersey annually on New Year's day.

DEVONSHIRE, EARLS AND DUKES OF. The Devonshire title, now in the Cavendish family, had previously been held by Charles Blount (1563-1606), 8th Lord Mountjoy, great-grandson of the 4th Lord Mountjoy (d. 1534), the pupil of Erasmus; he was created earl of Devonshire in 1603 for his services in Ireland, where he became famous in subduing the rebellion between 1600 and 1603; but the title became extinct at his death. In the Cavendish line the 1st earl of Devonshire was William (d. 1626), second son of Sir William Cavendish (q.v.), and of Elizabeth Hardwick, who afterwards married the 6th earl of Shrewsbury. He was created earl of Devonshire in 1618 by James I., and was succeeded by William, 2nd earl (1591-1628), and the latter by his son William (1617-1684), a prominent royalist, and one of the original members of the Royal Society, who married a daughter of the 2nd earl of Salisbury.

WILLIAM CAVENDISH, 1st duke of Devonshire (1640-1707), English statesman, eldest son of the earl of Devonshire last mentioned, was born on the 25th of January 1640. After completing his education he made the tour of Europe according to the custom of young men of his rank, being accompanied on his travels by Dr Killigrew. On his return he obtained, in 1661, a seat in parliament for Derbyshire, and soon became conspicuous as one of the most determined and daring opponents of the general policy of the court. In 1678 he was one of the committee appointed to draw up articles of impeachment against the lord treasurer Danby. In 1679 he was re-elected for Derby, and made a privy councillor by Charles II.; but he soon withdrew from the board with his friend Lord Russell, when he found that the Roman Catholic interest uniformly prevailed. He carried up to the House of Lords the articles of impeachment against Lord Chief-Justice Scroggs, for his arbitrary and illegal proceedings in the court of King's bench; and when the king declared his resolution not to sign the bill for excluding the duke of York, afterwards James II., he moved in the House of Commons that a bill might be brought in for the association of all his majesty's Protestant subjects. He also openly denounced the king's counsellors, and voted for an address to remove them. He appeared in defence of Lord Russell at his trial, at a time when it was scarcely more criminal to be an accomplice than a witness. After the condemnation he gave the utmost possible proof of his attachment by offering to exchange clothes with Lord Russell in the prison, remain in his place, and so allow him to effect his escape. In November 1684 he succeeded to the earldom on the death of his father. He opposed arbitrary government under James II. with the same consistency and high spirit as during the previous reign. He was withdrawn from public life for a time, however, in consequence of a hasty and imprudent act of which his enemies knew how to avail themselves. Fancying that he had received an insulting look in the presence chamber from Colonel Colepepper, a swaggerer whose attendance at court the king encouraged, he immediately avenged the affront by challenging the colonel, and, on the challenge being refused, striking him with his cane. This offence was punished by a fine of £30,000, which was an enormous sum even to one of the earl's princely fortune. Not being able to pay he was imprisoned in the king's bench, from which he was released only on signing a bond for the whole amount. This was afterwards cancelled by King William. After his discharge the earl went for a time to Chatsworth, where he occupied himself with the erection of a new mansion, designed by William Talman, with decorations by Verrio, Thornhill and Grinling Gibbons. The Revolution again brought him into prominence. He was one of the seven who signed the original paper inviting the prince of Orange from Holland, and was the first nobleman who appeared in arms to receive him at his landing. He received the order of the Garter on the occasion of the coronation, and was made lord high steward of the new court. In 1690 he accompanied King William on his visit to Holland. He was created marquis of Hartington and duke of Devonshire in 1694 by William and Mary, on the same day on which the head of the house of Russell was created duke of Bedford. Thus, to quote Macaulay, "the two great houses of Russell and Cavendish, which had long been closely connected by friendship and by marriage, by common opinions, common sufferings and common triumphs, received on the same day the highest honour which it is in the power of the crown to confer." His last public service was assisting to conclude the union with Scotland, for negotiating which he and his eldest son, the marquis of Hartington, had been appointed among the commissioners by Queen Anne. He died on the 18th of August 1707, and ordered the following inscription to be put on his monument:-

Willielmus Dux Devon,
Bonorum Principum Fidelis Subditus,
Inimicus et Invisus Tyrannis.

He had married in 1661 the daughter of James, duke of Ormonde, and he was succeeded by his eldest son William as 2nd duke, and by the latter's son William as 3rd duke (viceroy of Ireland, 1737-1744). The latter's son William (1720-1764) succeeded in 1755 as 4th duke; he married the daughter and heiress of Richard Boyle, earl of Burlington and Cork, who brought Lismore Castle and the Irish estates into the family; and from November 1756 to May 1757 he was prime minister, mainly in order that Pitt, who would not then serve under the duke of Newcastle, should be in power. His son William (1748-1811), 5th duke, is memorable as the husband of the beautiful Georgiana Spencer, duchess of Devonshire (1757-1806), and of the intellectual Elizabeth Foster, duchess of Devonshire (1758-1824), both of whom Gainsborough painted. His son William, 6th duke (1790-1858), who died unmarried, was sent on a special mission to the coronation of the tsar Nicholas at Moscow in 1826, and became famous for his expenditure on that occasion; and it was he who employed Sir Joseph Paxton at Chatsworth. The title passed in 1858 to his cousin William (1808-1891), 2nd earl of Burlington, as 7th duke, a man who, without playing a prominent part in public affairs, exercised great influence, not only by his position but by his distinguished abilities. At Cambridge in 1829 he was second wrangler, first Smith's prizeman, and eighth classic, and subsequently he became chancellor of the university.

SPENCER COMPTON CAVENDISH, 8th duke (1833-1908), born on the 23rd of July 1833, was the son of the 7th duke (then earl of Burlington) and his wife Lady Blanche Howard (sister of the earl of Carlisle). In 1854 Lord Cavendish, as he then was, took his degree at Trinity College, Cambridge; in 1856 he was attached to the special mission to Russia for the new tsar's accession; and in 1857 he was returned to parliament as Liberal member for North Lancashire. At the opening of the new parliament of 1859 the marquis of Hartington (as he had now become) moved the amendment to the address which overthrew the government of Lord Derby. In 1863 he became first a lord of the admiralty, and then under-secretary for war, and on the formation of the Russell-Gladstone administration at the death of Lord Palmerston he entered it as war secretary. He retired with his colleagues in July 1866; but upon Mr Gladstone's return to power in 1868 he became postmaster-general, an office which he exchanged in 1871 for that of secretary for Ireland. When Mr Gladstone, after his defeat and resignation in 1874, temporarily withdrew from the leadership of the Liberal party in January 1875, Lord Hartington was chosen Liberal leader in the House of Commons, Lord Granville being leader in the Lords. Mr W. E. Forster, who had taken a much more prominent part in public life, was the only other possible nominee, but he declined to stand. Lord Hartington's rank no doubt told in his favour, and Mr Forster's education bill had offended the Nonconformist members, who would probably have withheld their support. Lord Hartington's prudent management in difficult circumstances laid his followers under great obligations, since not only was the opposite party in the ascendant, but his own former chief was indulging in the freedom of independence. After the complete defeat of the Conservatives in the general election of 1880, a large proportion of the party would have rejoiced if Lord Hartington could have taken the Premiership instead of Mr Gladstone, and the queen, in strict conformity with constitutional usage (though Gladstone himself thought Lord Granville should have had the preference), sent for him as leader of the Opposition. Mr Gladstone, however, was clearly master of the situation: no cabinet could be formed without him, nor could he reasonably be expected to accept a subordinate post. Lord Hartington, therefore, gracefully abdicated the leadership, and became secretary of state for India, from which office, in December 1882, he passed to the war office. His administration was memorable for the expeditions of General Gordon and Lord Wolseley to Khartum, and a considerable number of the Conservative party long held him chiefly responsible for the "betrayal of Gordon." His lethargic manner, apart from his position as war minister, helped to associate him in their minds with a disaster which emphasized the fact that the government acted "too late"; but Gladstone and Lord Granville were no less responsible than he. In June 1885 he resigned along with his colleagues, and in December was elected for the Rossendale Division of Lancashire, created by the new reform bill. Immediately afterwards the great political opportunity of Lord Hartington's life came to him in Mr Gladstone's conversion to home rule for Ireland. Lord Hartington's refusal to follow his leader in this course inevitably made him the chief of the new Liberal Unionist party, composed of a large and influential section of the old Liberals. In this capacity he moved the first resolution at the famous public meeting at the opera house, and also, in the House of Commons, moved the rejection of Mr Gladstone's Bill on the second reading. During the memorable electoral contest which followed, no election excited more interest than Lord Hartington's for the Rossendale division, where he was returned by a majority of nearly 1500 votes. In the new parliament he held a position much resembling that which Sir Robert Peel had occupied after his fall from power, the leader of a small, compact party, the standing and ability of whose members were out of all proportion to their numbers, generally esteemed and trusted beyond any other man in the country, yet in his own opinion forbidden to think of office. Lord Salisbury's offers to serve under him as prime minister (both after the general election, and again when Lord Randolph Churchill resigned) were declined, and Lord Hartington continued to discharge the delicate duties of the leader of a middle party with no less judgment than he had shown when leading the Liberals during the interregnum of 1875-1880. It was not until 1895, when the differences between Conservatives and Liberal Unionists had become almost obliterated by changed circumstances, and the habit of acting together, that the duke of Devonshire, as he had become by the death of his father in 1891, consented to enter Lord Salisbury's third ministry as president of the council. The duke thus was the nominal representative of education in the cabinet at a time when educational questions were rapidly becoming of great importance; and his own technical knowledge of this difficult and intricate question being admittedly superficial, a good deal of criticism from time to time resulted. He had however by this time an established position in public life, and a reputation for weight of character, which procured for him universal respect and confidence, and exempted him from bitter attack, even from his most determined political opponents. Wealth and rank combined with character to place him in a measure above party; and his succession to his father as chancellor of the university of Cambridge in 1892 indicated his eminence in the life of the country. In the same year he had married the widow of the 7th duke of Manchester.

He continued to hold the office of lord president of the council till the 3rd of October 1903, when he resigned on account of differences with Mr BALFOUR (q.v.) over the latter's attitude towards free trade. As Mr Chamberlain had retired from the cabinet, and the duke had not thought it necessary to join Lord George Hamilton and Mr Ritchie in resigning a fortnight earlier, the defection was unanticipated and was sharply criticized by Mr Balfour, who, in the rearrangement of his ministry, had only just appointed the duke's nephew and heir, Mr Victor Cavendish, to be secretary to the treasury. But the duke had come to the conclusion that while he himself was substantially a free-trader,[1] Mr Balfour did not mean the same thing by the term. He necessarily became the leader of the Free Trade Unionists who were neither Balfourites nor Chamberlainites, and his weight was thrown into the scale against any association of Unionism with the constructive policy of tariff reform, which he identified with sheer Protection. A struggle at once began within the Liberal Unionist organization between those who followed the duke and those who followed Mr CHAMBERLAIN (q.v.); but the latter were in the majority and a reorganization in the Liberal Unionist Association took place, the Unionist free-traders seceding and becoming a separate body. The duke then became president of the new organizations, the Unionist Free Food League and the Unionist Free Trade Club. In the subsequent developments the duke played a dignified but somewhat silent part, and the Unionist rout in 1906 was not unaffected by his open hostility to any taint of compromise with the tariff reform movement. But in the autumn of 1907 his health gave way, and grave symptoms of cardiac weakness necessitated his abstaining from public effort and spending the winter abroad. He died, rather suddenly, at Cannes on the 24th of March 1908.

The head of an old and powerful family, a wealthy territorial magnate, and an Englishman with thoroughly national tastes for sport, his weighty and disinterested character made him a statesman of the first rank in his time, in spite of the absence of showy or brilliant qualities. He had no self-seeking ambitions, and on three occasions preferred not to become prime minister. Though his speeches were direct and forcible, he was not an orator, nor "clever"; and he lacked all subtlety of intellect; but he was conspicuous for solidity of mind and straightforwardness of action, and for conscientious application as an administrator, whether in his public or private life. The fact that he once yawned in the middle of a speech of his own was commonly quoted as characteristic; but he combined a great fund of common sense and knowledge of the average opinion with a patriotic sense of duty towards the state. Throughout his career he remained an old-fashioned Liberal, or rather Whig, of a type which in his later years was becoming gradually more and more rare.

There was no issue of his marriage, and he was succeeded as 9th duke by his nephew VICTOR CHRISTIAN CAVENDISH (b. 1868), who had been Liberal Unionist member for West Derbyshire since 1891, and was treasurer of the household (1900 to 1903) and financial secretary to the treasury (1903 to 1905); in 1892 he married a daughter of the marquess of Lansdowne, by whom he had two sons. (H. CH.)

[1] His own words to Mr Balfour at the time were: "I believe that our present system of free imports is on the whole the most advantageous to the country, though I do not contend that the principles on which it rests possess any such authority or sanctity as to forbid any departure from it, for sufficient reasons."

DEVONSHIRE (DEVON), a south-western county of England, bounded N.W. and N. by the Bristol Channel, N.E. by Somerset and Dorset, S.E. and S. by the English Channel, and W. by Cornwall. The area, 2604.9 sq. m., is exceeded only by those of Yorkshire and Lincolnshire among the English counties. Nearly the whole of the surface is uneven and hilly. The county contains the highest land in England south of Derbyshire (excepting points on the south Welsh border); and the scenery, much varied, is in most parts striking and picturesque. The heather-clad uplands of Exmoor, though chiefly within the borders of Somerset, extend into North Devon, and are still the haunt of red deer, and of the small hardy ponies called after the district. Here, as on Dartmoor, the streams are rich in trout. Dartmoor, the principal physical feature of the county, is a broad and lofty expanse of moorland which rises in the southern part. Its highest point, 2039 ft., is found in the north-western portion. Its rough wastes contrast finely with the wild but wooded region which immediately surrounds the granite of which it is composed, and with the rich cultivated country lying beyond. Especially noteworthy in this fertile tract are the South Hams, a fruitful district of apple orchards, lying between the Erme and the Dart; the rich meadow-land around Crediton, in the vale of Exeter; and the red rocks near Sidmouth. Two features which lend a characteristic charm to the Devonshire landscape are the number of picturesque old cottages roofed with thatch; and the deep lanes, sunk below the common level of the ground, bordered by tall hedges, and overshadowed by an arch of boughs. The north and south coasts of the county differ much in character, but both have grand cliff and rock scenery, not surpassed by any in England or Wales, resembling the Mediterranean seaboard in its range of colour. As a rule the long combes or glens down which the rivers flow seaward are densely wooded, and the country immediately inland is of great beauty. Apart from the Tamar, which constitutes the boundary between Devon and Cornwall, and flows into the English Channel, after forming in its estuary the harbours of Devonport and Plymouth, the principal rivers rise on Dartmoor. These include the Teign, Dart, Plym and Tavy, falling into the English Channel, and the Taw flowing north towards Bideford Bay. The river Torridge, also discharging northward, receives part of its waters from Dartmoor through the Okement, but itself rises in the angle of high land near Hartland point on the north coast, and makes a wide sweep southward. The lesser Dartmoor streams are the Avon, the Erme and the Vealm, all running south. The Exe rises on Exmoor in Somersetshire; but the main part of its course is through Devonshire (where it gives name to Exeter), and it is joined on its way to the English Channel by the lesser streams of the Culm, the Creedy and the Clyst. The Otter, rising on the Blackdown Hills, also runs south, and the Axe, for part of its course, divides the counties of Devon and Dorset. These eastern streams are comparatively slow; while the rivers of Dartmoor have a shorter and more rapid course.

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Encyclopaedia Britannica, 11th Edition, "Destructors" to "Diameter"Chapter IV: Part 4

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