Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/546

522 The best and only deep harbour on the coast is the well- protected roadstead inside of Ship Island. It has a depth of 27 feet, a firm clay bottom, and is readily accessible to lighters from the shallower harbours along the coast.

Climate. Near the waters of the Gulf of Mexico the climate is much milder than in the northern parts of the State. On the southern borders the temperature rarely falls to 32 Fahr. , or exceeds 95, the annual mean being about 68. The orange, lemon, almond, banana, and olive can be grown without protection. In the latitude of Vicksburg the temperature ranges from 98 to 20, very rarely lower ; the annual mean is 65. The range in the northern part of the State is from 98 to 15, or rarely 10, and the annual mean is 61. The first and last hoar-frosts occur, in the central parts of the State, usually in the latter parts of October and March. The ground is seldom frozen to the depth of 3 inches, and only for a few days at a time. The rainfall on the coast is 60 to 65 inches per annum, and at the northern boundary 50 inches. While about two-thirds of this precipitation occurs in winter and spring, a month seldom passes without several inches of rainfall.

Land and sea breezes in the south, and variable winds elsewhere, make the heat of summer tolerable. In healthfulness Mississippi compares favourably with other States. The average death-rate of thirteen States, variously situated, as given in the census of 1880, is 1 38 per cent. ; that of Mississippi is 1 - 19 per cent. Where the surface is flat and poorly drained malarial fevers are prevalent during the warm season. Yellow fever has become epidemic after importa tion, but strict quarantine has been successful in preventing it.

Geology. In accordance with an Act of the legislature passed in 1850, an agricultural and geological survey of the State was begun, which continued, with interruptions, until 1871. Two reports have been published, one in 1854 and another in 1860.

The geological structure of the State is comparatively simple, and closely related to that of the adjacent States. The older formations are nearly all overlaid by deposits of the Quaternary period, which will be described last. In the extreme north eastern portion are found the oldest rocks in the State, an ex tension of the Subcarboniferous formation which underlies the Warrior coal-fields of Alabama. The strata here show some traces of the upheaval which formed the Appalachian mountain chain, whose south-west termination is found in Alabama. When this chain formed the Atlantic mountain-border of the continent, except ing this north-east corner, Mississippi had not emerged from the waters of the ancient Gulf of Mexico. As the shore-line of the Gulf slowly receded southward and westward, the sediment at its bottom gradually came to the surface, and constituted the Cretaceous and Tertiary formations of this and adjacent States. Wherever stratification is observed in these formations in Mississippi, it shows a dip west and south of 20 or 30 feet to the mile. The Cretaceous region includes, with the exception of the Subcarboni ferous, all that part of the State eastward of a line cutting the Tennessee boundary in 89 3 W. long., and drawn southward and eastward through the towns of Ripley, Pontotoc, and Stark - ville, crossing into Alabama in latitude 32 45. Four groups of Cretaceous strata have been determined in Mississippi, defined by lines having the same general direction as the one just described. The oldest, bordering the Subcarboniferous, is the Eutaw or Coffee group, characterized by bluish-black or reddish laminated clays, and yellow or grey sands, containing lignite and fossil resin. Westward and southward to the city of Columbus is the Tombigbee sand group, consisting chiefly of fine-grained micaceous sands of a greenish tint, with many marine fossils. Next in order, westward and southward, is the Rotten Limestone group, made up of a material of great uniformity, a soft chalky rock, white or pale blue, composed chiefly of tenacious clay, and white carbonate of lime in minute crystals. Borings show the total thickness of this group to be about 1000 feet. Fossils are abundant, but species are few. The latest Cretaceous is the Ripley group, lying west of the northern part of the last-named group, and characterized by hard crystalline white limestones, and dark- coloured, micaceous, glauconitic marls, whose marine fossils are admirably preserved. One hundred and eighty species have been described. The total thickness of the Cretaceous is about 2000 feet. Deposits of the Tertiary period form the basis of more than half the State, extending from the border of the Cretaceous west ward nearly or quite to the Yazoo and Mississippi Bottom, and southward to within a few miles of the Gulf coast. Seven groups of the Tertiary strata have been distinguished. Beginning nearest the Cretaceous, the Flatwoods group is characterized by grey or white clays, and a soil which responds poorly to tillage. The Lagrange group, lying to the west of the last, is marked by grey clays and sands, fossil plants, and beds of lignite or brown coal, sometimes 8 feet in thickness. The Buhrstone group, lying south- westward from the last, is characterized by beds of white siliceous clays, and of silicified shells, and sandy strata containing glauconite in valuable quantities. The Claiborne group lies south of the last, and is slightly developed in Mississippi, but well-marked in Alabama. The Jackson group, south-west of the last two, is made up chiefly of soft yellowish limestones or marls, containing much clay, and sandy strata with glauconite. Zeuglodon bones and other marine fossils are abundant. The Vicksburg group lies next in order south-westward, and is characterized by crystalline limestones and blue and white marls. Marine fossils are very abundant. More than one hundred and thirty species have been determined. The Grand Gulf group, showing a few fossil plants and no marine fossils, extends southward from the last to within a few miles of the coast.

EB9 Mississippi (State) - geological map.jpg

The oldest formation of the Quaternary period is the &quot;orange sand&quot; or &quot;stratified drift,&quot; which immediately overlies all the Cretaceous groups except the prairies of the Rotten Limestone, and all the Tertiary except the Flatwoods and Vicksburg groups and parts of the Jackson. Its depth varies from a few feet to over 200 feet, and it forms the body of most of the hills in the State. Its materials are pebbles, clays, and sands of various colours from white to deep red, tinged with peroxide of iron, which sometimes cements the pebbles and sands into compact rocks. The shapes of these ferruginous sandstones are very fantastic, tubes, hollow spheres, plates, &c., being common. The name stratified drift is used by the geologist of Alabama to indicate its connexion with the northern drift. The fossils are few, and in some cases probably derived from the underlying formations. Well-worn pebbles of amorphous quartz, agate, chalcedony, jasper, &c., are found in the stratified drift along the western side of the Tertiary region of the State, and from Columbus northward. &quot;While this forma tion is not well understood, it seems tolerably well established that the melting of the great glaciers of the north furnished the water which brought with it fragments of the rocks over which it passed, and flowed into the Gulf with a current which was most rapid where the pebbles were dropped, but overspread the remainder of the State with a gentler flow, leaving sands and clays &quot; (E. A. Smith). The second Quaternary formation is the Port Hudson, occurring within 20 miles of the Gulf coast, and prob ably outcropping occasionally in the Mississippi Bottom. Clays, gravel, and sands, containing cypress stumps, drift-wood, and mastodon bones, are characteristic. The loess or bluff formation lies along the bluffs bordering the Bottom, nearly continuously through the State. Its fine-grained, unstratified silt contains the remains of many terrestrial animals, including fifteen mammals. 