Page:Encyclopædia Britannica, Ninth Edition, v. 6.djvu/74

Rh COAL [COAL. FIELDS. portions of the series are interstratifiecl with marine strata, containing fossils of Carboniferous and Devonian types. The same association is observed in the coal series of Bowen River in Queensland, and on those of the Mersey River in Tasmania, showing the extension of the Carboniferous strata in a chain of detached basins from the 20th to the 40th parallel of S. lat, or about 1400 miles. In Queensland the strata are estimated to cover an area of 24,000 square miles, without taking into account possible extension under the Cretaceous strata of the interior. Up to the present time, however, very little has been done towards their develop ment, the districts in which they occur being too far from the settled portions of the country. The principal mines now open are on newer strata of Cretaceous age nearer the sea, at Ipswich, in the neighbourhood of Brisbane. Some of these coals are remarkably like those of South Durham, and yield a good hard coke, suitable for blast-furnace purposes. New Zea- True coal measures are not known to exist in New Zea land- land, but coal-bearing strata of two different periods have been described by Dr Hector, Dr Haast, Captain Hutton, and other geologists. The newer series yield a lignite, which is described in the reports as hydrous coal ; while the older, which is probably of Cretaceous or Jurassic age, yields a superior class of combustible, known as anhydrous coal. These minerals occur at many different points in the two larger islands, and although no systematic detailed account of them is as yet available, a considerable amount of information on this subject is contained in the various geolo gical reports published by the New Zealand surveyors. North In North America, the Carboniferous strata are divided America, by geologists into two principal groups, the lower or sub-Carboniferous, which correspond to the Carboniferous limestone of Europe, and the Carboniferous, which includes the millstone grit and coal measures. The first of these is about 5000 feet thick in Penn sylvania, consisting mainly of shales and sandstones ; but in the Mississippi valley, in Illinois, Iowa, and Missouri, a considerable thickness of limestone is developed in this part of the series. In the former region some thin coal seams are found, the relation between the two areas being in this respect similar to that of the Carboniferous lime stone in England to the coal-bearing formations of similar age in Scotland. The millstone grit forms a mass of sandstones and conglomerates from 1200 to 1400 feet thick in Eastern Pennsylvania, but thins rapidly to the westward, being only from 100 to 250 feet thick in Ohio and Tennessee. In Arkansas, the compact siliceous rock known as novaculite, or Arkansas hone stone, occurs in this member of the Car boniferous series. The coal measures proper cover a very large area, both in the United States and in Canada. First in importance is the Appalachian coal-field, covering about 60,000 square miles, extending through parts of Pennsylvania, Ohio, Virginia, eastern Kentucky, Tennessee, and Alabama. The maximum thickness of strata is from 2500 to 3000 feet ; that of included coal is 120 feet near Pottsville, G2 feet at Wilkesbarre, and about 25 feet at Pittsburg, showin&quot; a gradual diminution to the westward. The most persistent coal is the Pittsburg seam, which is known over an area measuring 225 miles by 100 miles, but with a thickness varying from 2 to 1 4 feet. The anthracite district of central Pennsylvania occupies an area of about G50 miles on the left bank of the Susque- hanna River. The strata between Pottsville and Wyo ming, which belong to the lowest portion of the coal measures, are probably about 3000 feet thick, but it is difficult to arrive at an exact estimate, owing to the numerous folds and contortions. There are from ten to twelve seams above 3 feet in thickness ; the principal one, known as the Mammoth or Baltimore vein, is 29-| feet thick at Wilkesbarre, and in places even exceeds 60 feet. The Illinois and Missouri basin covers a considerable part of these States, as well as of Indiana and Kentucky, Iowa, Kansas, and Arkansas. Its area is estimated at 60,000 square miles, the thickness varying from 600 feet in Missouri to 3000 feet in western Kentucky. The aggregate thickness of coal is about 70 feet. A good furnace coal is obtained in Indiana, the so-called block coal of Brazil near Ind ianopolis, which, like the splint coals of Scotland and those of Staffordshire, can be used in the blast furnace without coking. In Michigan a nearly circular area of coal measures, of about 5000 square miles, occurs in the lower peninsula between lakes Huron and Erie. The thickness is only 120 feet, and the coals unimportant. Other coal-bearing areas of less value are known in Texas and Rhode Island. The Carboniferous strata are largely developed in the eastern provinces of the Dominion of Canada, notably ic New Brunswick and Nova Scotia. The lower Carbonifer ous group here consists of about 6000 feet of red sand stones and green marls, with thick beds of fossiliferous limestones, accompanied by gypsum. The limestones in crease in thickness southward. In this series occurs the peculiar pitch-like or asphaltic coal of the Albert mine in New Brunswick, of which an analysis is given in Table I., supra. The overlying coal measures, including the mill stone grit, occupy an area estimated at 18,000 square miles. The whole thickness of this group at South, Joggins is about 14,750 feet, with 76 included coal seams, together 45 feet in thickness, which are contained in the middle division of the series. At Pictou there are six seams, together measuring 80 feet in thickness. The coal measures in this area approach more near to the great coal fields of Europe in thickness than those of the other American Carboniferous districts. Rocks of Carboniferous age occur in various places on both flanks of the Rocky Mountains, and in the Arctic Archipelago, but have not yet been explored. Lignite-bearing strata of Cretaceous and Tertiary age occupy a very considerable area in the central and western portions of North America, especially in the upper Missouri and Saskatchewan valleys, in Utah and Texas, and in California, Oregon, and Vancouver Island. In the last locality coal has been extensively mined near Nanaimo, on the east coast, for several years past, in strata of Cretaceous age. Tertiary lignites are worked in Belling- ham Bay, at Goose Bay in Oregon, and at Monte Diabolo, near San Francisco. The lignitic formations of the eastern flank of the Rocky Mountains, which are considered by Hayden to occupy a position between the Cretaceous and Eocene Tertiary strata, occupy an area estimated at about 50,000 square miles within the United States, and extend both northward into Canada and southward into Mexico. In South America coal, probably of Carboniferous age, South is found in the Brazilian provinces of Sao Pedro, Rio Americ Grande do Sul, and Santa Catharina, and in the neighbouring state of Uraguay. The largest area is that known as the Candiota coal-field, which is exposed for about 50 miles in the valley of the river of the same name. The sections ex posed show 5 seams from 9 to 25 feet each, or together about 65 feet of coal. Other basins are known at S. Sepe&quot; and S. Jeronimo, on the Jacahahay River. The latter is the only point at which mines are worked, as the coals, though thinner than those of the other localities mentioned, are situated within the reach of navigable waters, having only to bear a land carriage of 8 miles to the river.