Chapter 35 of 47 · 3949 words · ~20 min read

Part 35

_Cambrian Stratigraphy._--Wherever the Cambrian strata have been carefully studied it has now been found possible and convenient to arrange them into three series, each of which is characterized by a distinctive genus of trilobite. Thus we have a Lower Cambrian with _Olenellus_, a middle series with _Paradoxides_ and an Upper Cambrian with _Olenus_. It is true that these fossils are not invariably present in every occurrence of Cambrian strata, but this fact notwithstanding, the threefold division holds with sufficient constancy. An uppermost series lies above the _Olenus_ fauna in some areas; it is represented by the Tremadoc beds in Britain or by the _Dictyonema_ beds or _Euloma-Niobe_ fauna elsewhere. Three regions deserve special attention: (1) Great Britain, the area in which the Cambrian was first differentiated from the old "Transition Series"; (2) North America, on account of the wide-spread occurrence of the rocks and the abundance and perfection of the fossils; and (3) Bohemia, made classic by the great labours of J. Barrande.

_Great Britain and Ireland._--The table on p. 88 contains the names that have been applied to the subdivisions of the Cambrian strata in the areas of outcrop in Wales and England; at the same time it indicates approximately their relative position in the system.

In _Scotland_ the upper and middle series are represented by a thick mass of limestone and dolomite, the Durness limestone (1500 ft.). In the lower series are, in descending order, the "Serpulite grits" or "Salterella beds," the "Fucoid beds" and the "Eriboll quartzite," which is divided into an upper "Pipe rock" and lower "Basal quartzite."

The Cambrian rocks of _Ireland_, a great series of purple and green shales, slates and grits with beds of quartzite, have not yet yielded sufficient fossil evidence to permit of a correlation with the Welsh rocks, and possibly some parts of the series may be transferred in the future to the overlying Ordovician.

_North America._--On the North American continent, as in Europe, the Cambrian system is divisible into three series: (1) the lower or "Georgian," with _Olenellus_ fauna; (2) the middle or "Acadian," with _Paradoxides or Dikelocephalus_ fauna; (3) the upper or "Potsdam," with _Olenus_ fauna (with Saratogan or St Croix as synonyms for Potsdam). The lower division appears on the Newfoundland and Labrador coasts, and is traceable thence, in a great belt south-west of those points, through Maine and the Hudson-Champlain valley into Alabama, a distance of some 2000 m.; and the rocks are brought up again on the western uplift, in Nevada, Idaho, Utah, western Montana and British Columbia. The middle division covers approximately the same region as the lower one, and in addition it is found in the states of Texas, Oklahoma, and Arizona, in western Montana, and possibly in western Wisconsin. The lower division, in addition to covering the areas already indicated, spreads over the interior of the United States.

_Bohemia_.--The Cambrian rocks of this country are now recognized by J.F. Pompesk; to comprise the Paradoxidian and Olenelledian groups. They were made famous through the researches of Barrande. The Cambrian system is covered by his stages "B" and "C"; the former a barren series of conglomerates and quartzites, the latter a series of grey and green fissile shales 1200 ft. thick with sandstones, greywackes and conglomerates.

_Scandinavia_.--Here the Cambrian system is only distinguished clearly on the eastern side, where the three subdivisions are found in a thin series of strata (400 ft.), in which black concretion-bearing shales play an important part. Limestones and shales with the _Euloma-Niobe_ fauna come at the top. The upper series (_Olenus_) has been minutely zoned by W.C. Brögger, S.A. Tullberg and J.C. Moberg. In the middle series (_Paradoxides_) three thin limestone bands have been distinguished, the Fragmenten-Kalk, the Exulans-Kalk and the Andrarums-Kalk.

On the Norwegian side the Cambrian is perhaps represented by the Röros schists which lie at the base of a great series of crystalline schists, the probable equivalent of Ordovician and Silurian rocks.

_Baltic Province._--The Cambrian rocks in this region are nearly all soft sediments, some 600 ft. thick; they reach from the Gulf of Finland towards Lake Ladoga. At the base is the so-called "blue clay" (really greenish) with ferruginous sandstones and with a fucoidal sandstone at its summit. This division is the equivalent of the Lower Cambrian. Above the fucoidal sandstone an important break appears in the system, for the _Paradoxides_ and _Olenus_ divisions are absent. The upper members are the "Ungulite grit" and about 20 ft. of Dictyonema shale. Cambrian rocks have been traced into Siberia (lat. 71°) and on the island of Vaigatch.

_Central Europe._--Besides the Bohemian region previously mentioned, Cambrian rocks are present in Belgium and the north of France, in Spain and the Thüringer Wald. In the Ardennes the system is represented by grits and sandstones, shales, slates and quartz schists, and includes also whet slates and some igneous rocks. A. Dumont has arranged the whole series (_Terrain ardennais_) into three systems, an upper "Salmien," a middle "Revinien" and a lower "Devillien," but J. Gosselet has subsequently proposed to unite the two lower groups in one.

_France_.---In northern France Cambrian rocks, mostly purple conglomerates and red shales, rest with apparent unconformability upon pre-Cambrian strata in Brittany, Normandy and northern Poitou. In the Rennes basin limestones--often dolomitic--are associated with quartzites and conglomerates; silicious limestones also occur in the Sarthe region. Farther south, around the old lands of Languedoc, equivalents of the two upper divisions of the Cambrian have been recorded; and the uppermost members of the system appear in Herault. Patches of Cambrian rocks are found in the Pyrenees.

In _Spain_ slates and quartzites, the slates of Rivadeo, more than 9000 ft. thick, are followed by the middle Cambrian beds of La Vega, thick quartzites with limestone, slates and iron ores. Cambrian rocks occur also in the provinces of Seville and Ciudad-Real. Upper Cambrian strata have been found in upper Alemtejo in Portugal.

In _Russian Poland_ is a series of conglomerates, quartzites and shales; Some of the beds yield a _Paradoxides_ fauna.

In the _Thüringer Wald_ are certain strata, presumably Cambrian since the uppermost beds contain the _Euloma-Niobe_ fauna.

_Sardinia_ contains both middle and upper Cambrian. The Cambrian system is represented in the Salt Range of India by the Neobolus or Khussack beds, which may possibly belong to the middle subdivision. The same group is probably represented in Corea and the Liao-tung by the thick "Sinisian" formation of F. von Richthofen.

In _South America_ upper Cambrian rocks have been recorded from north Argentina.

The Lower Cambrian has been found at various places in _South Australia_; and in _Tasmania_ a thick series of strata appears to be in part at least of Upper Cambrian age.

_General Physical Conditions in the Cambrian Period._--The Cambrian rocks previously described are all such as would result from deposition, in comparatively shallow seas, of the products of degradation of land surfaces by the ordinary agents of denudation. Evidences of shallow water conditions are abundant; very frequently on the bedding surfaces of sandstones and other rocks we find cracks made by the sun's heat and pittings caused by the showers that fell from the Cambrian sky, and these records of the weather of this remote period are preserved as sharply and clearly as those made only to-day on our tidal reaches. Ripple marks and current bedding further point, to the shallowness of the water at the places where the rocks were made.

No Cambrian rocks are such as would be formed in the abysses of the sea--although the absence of well-developed eyes in the trilobites has led some to assume that this condition was an indication that the creatures lived in abyssal depths.

At the close of the pre-Cambrian, many of the deposits of that period must have been elevated into regions of fairly high ground; this we may assume from the nature of the Cambrian deposits which are mainly the product of the denudation of such ground. Over the land areas thus formed, the seas in Cambrian time gradually spread, laying down first the series known as Lower Cambrian, then by further encroachment on the land the wider spread Upper Cambrian deposits--in Europe, the middle series is the most extensive. Consequently, Cambrian strata are usually unconformable on older rocks.

During the general advance of the sea, local warpings of the crust may have given rise to shallow lagoon or inland-lake conditions. The common occurrence of red strata has been cited in support of this view.

Compared with some other periods, the Cambrian was free from extensive volcanic disturbances, but in Wales and in Brittany the earlier portions of this period were marked by voluminous outpourings; a condition that was feebly reflected in central and southern Europe.

No definite conclusions can be drawn from the fossils as to the climatic peculiarities of the earth in Cambrian times. The red rocks may in some cases suggest desert conditions; and there is good reason to suppose that in what are now Norway and China a glacial cold prevailed early in the period.

Considerable variations occur in the thickness of Cambrian deposits, which may generally be explained by the greater rapidity of deposition in some areas than in others. Nothing could be more striking than the difference between the thicknesses in western and eastern Europe; in Brittany the deposits are over 24,000 ft. thick, in Wales at least 12,000 ft., in western England they are only 3000 ft., and in northern Scotland 2000 ft., while no farther east than Scandinavia the complete Cambrian succession is only about 400 ft. thick. Again, in North America, the greatest thicknesses are found along the mountainous regions on the west and on the east--reaching 12,000 ft. in the latter and probably nearly 40,000 ft. in the former (in British Columbia)--while over the interior of the continent it is seldom more than 1000 ft. thick.

Any attempt to picture the geographical conditions of the Cambrian period must of necessity be very imperfect. It was pointed out by Barrande that early in Palaeozoic Europe there appeared two marine provinces--a northern one extending from Russia to the British Isles through Scandinavia and northern Germany, and a southern one comprising France, Bohemia, the Iberian peninsula and Sardinia. It is assumed that some kind of land barrier separated these two provinces. Further, there is a marked likeness between the Cambrian of western Europe and eastern America; many fossils of this period are common to Britain, Sweden and eastern Canada; therefore it is likely that a north Atlantic basin existed. Prof. Kayser suggests that there was also a Pacific basin more extensive than at present; this is borne out by the similarity between the Cambrian faunas of China, Siberia and Argentina. The same author postulates an Arctic continent, bordering upon northern Europe, Greenland and North America; an African-Brazilian continent across the present south Atlantic, and a marine communication between Australia and India, where the faunas have much in common.

REFERENCES.--The literature devoted to the Cambrian period is very voluminous, important contributions having been made by A. Sedgwick, Sir R.I. Murchison, H. Hicks, C. Lapworth, T. Groom, J.W. Salter, J.E. Marr, C.D. Walcott, G.F. Matthew, E. Emmons, E. Billings, J. Barrande, F. Schmidt, W.C. Brögger, S.A. Tullberg, S.L. Torngrist, G. Linnarsson and many others. A good general account of the period will be found in Sir A. Geikie's _Text-Book of Geology_, vol. ii. 4th ed. 1903 (with references), and from an American point of view, in T.C. Chamberlin and R.D. Salisbury's _Geology_, vol. ii., 1906 (references to American sources). See also J.E. Marr, _The Classification of the Cambrian and Silurian Rocks_, 1883 (with bibliography up to the year of publication); A. Geikie _Q.J. Geol. Sac.,_ 1891, xlvii., Ann. address, p. 90; F. Frech, "Die geographische Verbreitung und Entwickelung des Cambrium," _Compte Rendu. Congrès Géol. Internal. 1897, St-Pétersbourg_ (1899); _Geological Literature added to the Geological Society's Library,_ published annually since 1893. (J. A. H.)

CAMBRIC, a word derived from _Kameryk_ or _Kamerijk_, the Flemish name of Cambrai, a town in the department of Nord, France, where the cloth of this name is said to have been first made. It was originally made of fine linen. There is a record of a privy purse expenditure in 1530 for cambric for Henry VIII.'s shirts. Cambric has been used for many years in the manufacture of handkerchiefs, collars, cuffs, and for fine underclothing; also for the best shrouds, and for fine baby linen. The yarns for this cloth are of very fine quality, and the number of threads and picks often reaches and sometimes exceeds 120 per inch. Embroidery cambric is a fine linen used for embroidery. Batiste, said to be called after Baptiste, a linen-weaver of Cambrai, is a kind of cambric frequently dyed or printed. All these fabrics are largely copied in cheaper materials, mixtures of tow and cotton, and in many cases cotton alone, taking the place of the original flax line yarns.

CAMBRIDGE, EARLS AND DUKES OF. Under the Norman and early Plantagenet kings of England the earldom of Cambridge was united with that of Huntingdon, which was held among others by David I., king of Scotland, as the husband of earl Waltheof's daughter, Matilda. As a separate dignity the earldom dates from about 1340, when William V., count (afterwards duke) of Juliers, was created earl of Cambridge by King Edward III.; and in 1362 (the year after William's death) Edward created his own son, Edmund of Langley, earl of Cambridge, the title being afterwards merged in that of duke of York, which was bestowed upon Edmund in 1385. Edmund's elder son, Edward, earl of Rutland, who succeeded his father as duke of York and earl of Cambridge in 1402, appears to have resigned the latter dignity in or before 1414, as in this year his younger brother, Richard, was made earl of Cambridge. In the following year Richard was executed for plotting against King Henry V., and his title was forfeited, but it was restored to his son, Richard, who in 1415 became duke of York in succession to his uncle Edward. Subsidiary to the dukedom of York the title was held by Richard, and after his death in 1460 by his son Edward, afterwards King Edward IV., becoming extinct on the fall of the Yorkist dynasty.

In 1619 King James I., anxious to bestow an English title upon James Hamilton, 2nd marquess of Hamilton (d. 1625), created him earl of Cambridge, a title which came to his son and successor James, 3rd marquess and first duke of Hamilton (d. 1649). In 1651 when William, 2nd duke of Hamilton, died, his English title became extinct.

Again bestowed upon a member of the royal house, the title of earl of Cambridge was granted in 1659 by Charles II. to his brother Henry, duke of Gloucester, only to become extinct on Henry's death in the following year. In 1661 Charles, the infant son of James, duke of York, afterwards King James II., was designated as marquess and duke of Cambridge, but the child died before the necessary formalities were completed. However, two of James's sons, James (d. 1667) and Edgar (d. 1671), were actually created in succession dukes of Cambridge, but both died in childhood. After the passing of the Act of Settlement in 1701 it was proposed to grant an English title to George Augustus, electoral prince of Hanover, who, after his grandmother, the electress Sophia, and his father, the elector George Louis, was heir to the throne of England; and to give effect to this proposal George Augustus was created marquess and duke of Cambridge in November 1706. The title lapsed when he became king of Great Britain and Ireland in 1727, but it was revived in 1801 in favour of Adolphus Frederick, the seventh son of George III. He and his son are dealt with below.

ADOLPHUS FREDERICK, duke of Cambridge (1774-1850), was born in London on the 24th of February 1774. Having studied at the university of Göttingen, Adolphus Frederick served in the Hanoverian and British armies, and, in November 1801, was created earl of Tipperary and duke of Cambridge, becoming a member of the privy council in the following year. The duke is chiefly known for his connexion with Hanover. In 1815, on the conclusion of the war, the electorate of Hanover was raised to the rank of a kingdom, and in the following year the duke was appointed viceroy. He held this position until the separation of Great Britain and Hanover in 1837, and displaying tact and moderation, appears to have ruled the country with great success during a difficult period. Returning to England the duke became very popular, and was active in supporting many learned and benevolent societies. He died in London on the 8th of July 1850. In 1818 he married Augusta (1797-1889), daughter of Frederick, landgrave of Hesse-Cassel. He left three children: his successor, George; Augusta Caroline (b. 1822), who married Frederick William, grand duke of Mecklenburg-Strelitz; and Mary Adelaide (1833-1897), who married Francis, duke of Teck.

GEORGE WILLIAM FREDERICK CHARLES, duke of Cambridge (1819-1904), was born at Hanover on the 26th of March 1819. He was thus about two months older than his cousin, Queen Victoria, and was for that period in the line of succession to the British throne. He was educated at Hanover by the Rev. J.R. Wood, a canon of Worcester. In November 1837, after he had served for a short time in the Hanoverian army, the rank of colonel in the British army was conferred upon him, and he was attached to the staff at Gibraltar from October 1838 to April 1839. After serving in Ireland with the 12th Royal Lancers, he was appointed in April 1842 colonel of the 17th Light Dragoons (now Lancers). From 1843 to 1845 he was colonel on the staff in the Ionian Islands, and was then promoted major-general. In October 1846 he took command of the Limerick district, and shortly afterwards of the Dublin district. In 1850 his father died, and he succeeded to the dukedom. Being appointed inspector of cavalry in 1852, he held that post until 1854, when, upon the outbreak of the Crimean War, he was placed in command of the 1st division (Guards and Highland brigades) of the British army in the East. In June of the same year he was promoted lieutenant-general. He was present at the battles of the Alma, Balaklava and Inkerman, and at the siege of Sevastopol. On the 15th of July 1856 he was appointed general commanding-in-chief, on the 9th of November 1862 field marshal, and by letters patent, 1887, commander-in-chief. The long period during which he held the command of the army was marked by many changes. The Crimean War brought to light great administrative defects, and led to a regrouping of the departments, which, with the whole personnel of the army, were brought under the authority of the secretary of state for war. The constitutional changes involved did not, however, affect seriously the organization of the military forces. Only in 1870, after the successes of Prussia had created a profound impression, were drastic changes introduced by Cardwell into the entire fabric of the army. The objects of the reformers of 1870 were undoubtedly wise; but some of the methods adopted were open to question, and were strongly resented by the duke of Cambridge, whose views were shared by the majority of officers. Further changes were inaugurated in 1880, and again the duke found much to criticize. His opinions stand recorded in the voluminous evidence taken by the numerous bodies appointed to inquire into the condition of the army. They show a sound military judgment, and, as against innovations as such, a strong attachment to the old regimental system. That this judgment and this attachment were not so rigid as was generally supposed is proved by his published correspondence. Throughout the period of change, while protesting, the duke invariably accepted and loyally endeavoured to carry out the measures on which the government decided. In a memorandum addressed to Mr Childers in 1880 he defined his attitude as follows:--"Should it appear, however, that for reasons of state policy it is necessary that the contemplated changes should be made, I am prepared to carry them out to the best of my ability." This attitude he consistently maintained in all cases in which his training and associations led him, rightly or wrongly, to deprecate changes the need for which was not apparent to him. His judgment was especially vindicated in the case of an ill-advised reduction of the artillery carried out by Mr. Stanhope. Under the order in council of February 1888, the whole responsibility for military duties of every kind was for the first time centred upon the commander-in-chief. This, as pointed out by the Hartington commission in 1890, involved "an excessive centralization" which "must necessarily tend to weaken the sense of responsibility of the other heads of departments, and thus to diminish their efficiency." The duke of Cambridge, whose position entailed many duties apart from those strictly appertaining to a commander-in-chief, could not give personal attention to the vast range of matters for which he was made nominally responsible. On the other hand, the adjutant-general could act in his name, and the secretary of state could obtain military advice from officials charged with no direct responsibility. The effect was to place the duke in a false position in the eyes of the army and of the country. If the administration of the army suffered after 1888, this was due to a system which violated principles. His active control of its training during the whole period of his command was less hampered, and more directly productive of good results.