Its waters however have been rendered available by the construction of canals. Some of the affluents of the Susquehanna, as the Tioga, Juniata, and Salaam, are navigable for small boats, at least a con siderable part of the year, when the rivers are fulL The western part of the state is drained by the two principal branches of the Ohio, the Allegheny and Monongahela rivers. plisetsstert RIVER, vol. iii. eoL 821.) Both of these rivers are navi gable fur boats during several months of the year. The Ohio, also noticed under MIS1119111PPI Raven, is formed by the junction of these two streams, and runs westward about 40 miles through Pennsylvania; it is joined from the north by the Big Beaver River, which is navigable for boats as far as the boundary-line betwoen Pennsylvania and the Ohio.
Pennsylvania has a most extensive system of canals, by which the great coal fields el the state, sal Its commercial. manufacturing, and agricultural districts are provided with abundant facilities of internal water oommassiestiost, and connected with Lake Erie on the one side, ash PhDs&JOAN New York, and the Atlantic on the other. The rails Bass fee the most part follow the great valleys of the Interior. la sU them are above 1100 miles of canal in the states The railways of Pesarryleanis are of great extant and Importance; and they are of a more costly character than those of any other state eleept New York. The longest lines are those carried quite across the state, from Philadelphia westward by Harrisburg to Pittsburg. and thews to Crestline in Ohio; and the unfinished series Intended to run from Plelladephla north-westward by way of Sunbury to Lake Erie; while other main and junction lines of considerable length and las mantet all the leading towns of the state with each other.
with the towns on the linos of railway belonging to the neigh bouring states. On theist of January 1S55, there were in Pennsylvania 1991 miles of railway In operation, and 1100 miles in progress or pro jected. Tha number of railways was 60; but many of those are merely *hart mineral lines constructed for conveying the coal, &c., from the pita to the ordinary passenger lines.
Geolegy, Mineralogy, etc—Igneous and metamorphic rocks occupy the south-eastern portion of the state. In the extreme south-east angle they are chiefly of granite, sienito, &c.; but north of these the lent rocks of this series are of ameba, mica-achiat, talcose slate, crystalline limestone, &c.; whilst veins of copper trap occur in several places. Bordering these on the west and north is a belt of Lower Saurian strata, which stretches across the state from Maryland to the Delaware above Trenton, and consists of thick beds of dark reddish brown argillamous sandstone, compact limestone, and over all slaty clays. West and north of this series and following its outliue is a
narrower belt of Upper Silurian strata, consisting chiefly of light gray limestones. Beyond these occur widely extended strata of Devonian rocks. These occupy the middle and north-eastern part of the state, attain a depth of some 14,000 feet, and consist of very fossiliferous sandstones, thick beds of marl and clay, and enrmounting all strata of very deep red-sandatone, corresponding to the Old Red-Sandstone of Wales and Scotland. The whole of the western half of Pennsylvania belongs to the Carboniferous system—a portion of the great coal-field of the Alleghenies. The Dower Carboniferous strata are chiefly repre sented by red whist and siliceous conglomerate, and form a narrowish band west of the Devonian rocks, and between them and the Upper taerboniferous strata, or coal -measures, which occupy the entire remaining portion of the state, and recur in detached patches through out the district assigned to the Devonian formation • it is indeed among these detached portions that the most coal-mines occur. The Upper Carboniferous strata consist chiefly of conglo merate as the bare of the formation, and above carboniferous limestone, sandstone, and clay-slates, with veins of Erne coal, both bituminous and anthracite.
Rich as Pennsylvania is in minerals, by far the most important is coal. The anthracite coal is found in the greatest quantity between the Blue Ridge and the Susquehanna River, and chiefly in the Lehigh and Iseckswaona valleys. The richest mines are near Mount Carbon or Pottsville, on the Schuylkill, and near Mauch Chunk on the Lehigh, where beds occur above 40 feet thick, and are worked in the open air, the overlying sandstone, 40 feet thick, having been removed bodily from the top of the hill. The quantity of coal extracted from the Schuylkill field in 1851 amounted to 2,178,584 tons. Other very productive beds of anthracite occur in the Wyoming valley and else where. The bituminous coal-fields of Pennsylvania lie in the western party of the state, where the coal is found in beds varying in thickness from an Inch to six feet and upwards : and it is noteworthy that the coal become' progressively bituminous as we advance westward in the Mate. The coal-lands of Pennsylvania are said to occupy above 15,000 square miles, or nearly one-third of the entire area of the state. The quantity of coal now annually obtained from the coal-mines or quarries of Pennsylvania averages nearly 6,000,000 tone, of which about 1,300,000 tons are bituminous.