The American Cyclopædia (1879)/Bog

BOG, an Irish word, literally meaning soft, applied in Great Britain to extensive districts of marshy land. In Europe these tracts consist so generally of peat, that this substance is there regarded as essential to a bog. True bogs are most commonly found in northern latitudes, and in districts where great humidity prevails. Their situation is not necessarily low, nor their surface level, some of the great Irish bogs presenting even a hilly appearance. In places naturally moist, by the abundance of springs, or around shallow ponds, the mosses, lichens, heaths, and grasses flourish, which by their spread produce the great peat bogs, or mosses. They encroach upon the ponds and fill them up with luxuriant living vegetation and the accumulations of decayed matter. The moss called sphagnum palustre grows most abundantly, and, like the coral in the ocean, the new growth above leaves the lower portion below dead and buried. The famous levels of Hatfield Chase in Yorkshire, which were stripped of their forests by the Romans, were cleared up in the latter part of the 17th century, when vast quantities of excellent timber were found buried beneath the morass. Many of the trees were of extraordinary size, some larger than any now known in Great Britain. Many of them retained the marks of the axe, and some still held the wooden wedges used to rend them. Broken axe heads were discovered, links of chains, and coins of Vespasian and other Roman emperors. The great cedar swamps in the southern part of New Jersey also retain in their peaty soil much valuable timber, the relics of forests of unknown age. An extensive business has long been carried on in extracting this ancient timber and converting it into shingles. The logs are discovered by thrusting an iron rod down through the mud, till one is struck and traced along its length. Some have been found 30 ft. long, and 4, 5, and 6 ft. in diameter, and one of 7 ft. They retain their buoyancy, and float with the side uppermost which was in the swamp the under one. Bogs covered with living forests, like these cedar swamps, receive new accumulations of vegetable matters from the continual waste of their foliage and of the smaller shrubs, which grow among the trees. The forests, once swept off by fire or other cause, are seldom restored. The waters, obstructed by the trunks and branches, stagnate; the mosses then take possession of the surface, and unless this is drained, the spongy covering increases in the manner already described.—In most northern countries bogs are met with of vast extent and in great numbers. They cover such large districts, that they possess a geographical importance, while the materials of which they are composed give them no little geological interest, from the light they shed upon the mode of formation of the more ancient carboniferous deposits of the coal measures. The great peat marsh of Montoire in France, near the mouth of the Loire, is said to have a circumference of 50 leagues. This is somewhat larger than the Great Dismal swamp of Virginia and North Carolina, and but little inferior to the area covered by the swamps that make up the Okefinokee in Georgia, said to be about 180 miles in circumference. But the central portion of Ireland is the great region of bogs. Upon a map of the island is seen, between Sligo and Galway bay, a portion on the western coast, projecting into the ocean from the main body of the island. A strip of this width, extended in an easterly direction across the country, includes about one fourth of the area of the island, and in this portion are found about six sevenths of its bogs, leaving out of the account the small ones not exceeding about 800 acres each. The whole amount of bog surface is 2,831,000 acres, nearly all of which forms one almost connected mass. The great bog of Allen, E. of the Shannon, extends 50 m. in length by 2 to 3 in breadth. This is divided by occasional high lands into several bogs. They all consist of peat, averaging about 25 ft. in thickness, never less than 12 nor more than 42. The upper 10 ft. is composed of a mass of the fibres of the mosses, more or less decomposed, and a light turf of blackish brown color underlies this, in which the fibres of moss may still be perceived. This variety may extend 10 ft. deeper. “At a greater depth the fibres of vegetable matter cease to be visible, the color of the turf becomes blacker, and the substance much more compact, its properties as fuel more valuable, and gradually increasing in the degree of blackness and compactness proportionate to its depth; near the bottom of the bog it forms a black mass, which when dry has a strong resemblance to pitch or bituminous coal, having a conchoidal fracture in every direction, with a black, shining lustre, and susceptible of receiving a considerable polish.” (Report of surveyors appointed by parliament, 1810.) In England the largest lowland bog is Chatmoss in Lancashire. It is 6 m. long, 3 m. in greatest breadth, and contains 7,000 acres. It is a mass of pure vegetable matter, without any mixture of sand, gravel, or other material, from 10 to 30 ft. in depth. It is noted for the engineering difficulties it offered to the passage of the first great English railway. George Stephenson carried the Liverpool and Manchester railway over it when all other engineers considered the task impossible.—In the Great Dismal swamp of Virginia and North Carolina, the extent of which is about 40 m. N. and S. and 25 m. E. and W., little true peat appears to be found. The soil is perfectly black, consisting wholly of vegetable matter to the depth of about 15 ft. When dug up and exposed at the surface, it rapidly decomposes. The surface is covered with mosses, reeds, ferns, and aquatic trees and shrubs. The white cedar is abundant as in all our swamps, and they and the tall cypress furnish timber of such value, that the inmost recesses of this tangled morass have been penetrated by canals in search of it. In its central portion the surface is found to be 12 ft. higher than the rest, and the general level of the swamp is above that of the adjoining country. Throughout the country, along the seaboard to the gulf of Mexico, swamps of this character are of frequent occurrence. The outer portions are sometimes wooded swamps, while within they present moss-covered heaths, stretching, like the western prairies, further than the eye can see, and dotted occasionally with clumps or little islands of trees. In New England, the northwestern states, and Canada, the bogs furnish genuine peat, and some of those bordering the great lakes are of great extent. Over one of these the traveller is carried upon the Great Western railroad in Canada, between Chatham and Lake St. Clair. Upon Long Island, near New York city, the bogs present a marked feature along the sandy coast, and their structure was finely exposed in the excavations made for the Brooklyn aqueduct. Here, as elsewhere, they are found to be the repositories of the remains of the mastodon. (See Alluvium, and Peat.)