BOERHAAVIA, a genus of plfuits named after the celebrated Boerhaave, belonging to the natural order Nyctagineess. The species of .Boerhaaria have generally emetic and purgative properties, and have been employed medicinally both by the natives of Peru and the East Indies, where the species grow. B. tularosa is stated by Lindley to be the Yerba de la Purgation of Peru, and that it is employed as a culinary vegetable. The root of B. decumbens is called Hog-Meat in Jamaica, and on account of its emetic properties it is sometimes called Ipecacuauha in Guyana. Sir Robert Schomburgh states that it is astringent, and is useful in dysentery. B. decumbens and B. birstaa are also said to possess medicinal properties. (Lindley, Vegetable Kingdom.) BOG. The name of Bog has been given indiscriminately to very different kinds of substances. In all cases the expression signifies mum earthy substance wanting in firmness or consistency, which state seems to arise generally (perhaps not always) from the presence of a superabundant supply of moisture having no natural outlet or drain.
In some cases, where springs of water, or the drainage from an extensive area, are pent up near the surface of the soil, they simply render it soft or boggy, and in this state the land is perhaps more properly called a Quagmire. A second state of bog is where, in addition to the condition just described, a formation of vegetable matter is induced, which dying and being reproduced on the surface assumes the state of a spongy mass of sufficient consistence to bear a considerable weight. Bogs of this description are numerous and extensive in Ireland, where they are valuable from the use made of the solid vegetable matter, both as fuel and as a principal ingredient in composts for manures. Where the turf has been cut away for these purposes, several bogs have been reclaimed by draining ; and tho subsoil is then readily brought into cultivation. Bogs also occur in all parts of Great Britain where the form of the surface and the nature of the earth favour the general condition under which bog is formed. Thus there are bogs on the high granitic plateau of Cornwall, on the road from Launceston to Bodmin ; and in the large granitic mass, of which Brown Willy is the centre, the bottoms of the valleys are covered with bogs, the lower part of which is consolidated into peat. Although peat-moss always springs from some moist spot, it will grow and spread over sound ground, and if not stopped by.
some natural or artificial impediment, such as a wall, would overrun whole districts. In this ease it absorbs any moisture which reaches it, and retains it like a sponge.
The depth of a bog depends on the level of the surrounding grounds. It cannot rise much higher than the lowest outlet for the water. Where there is no immediate outlet the bog increases, until the evaporation is equal to the supply of the springs and rains, or till it rises to a level with its lowest boundary, where it becomes the source of a stream or river, and forms a lake. The mud being deposited at the bottom, gradually becomes a true peat, or is quite reduced to its elementary earths. In this case it may become a stratum of rich alluvial soil, which some convulsion of nature may lay dry for the benefit of future ages. From this circumstance has arisen the great advantage of draining bogs, to which the attention of agriculturists and men of science has often been profitably directed.
The bogs of Ireland are estimated in the whole to exceed in extent 2,800,000 English acres. The greater part of these bogs may be con sidered as forming one connected mass. If a line were drawn from Wicklow-Head on the east coast to Galway, and another line from also on the east coast, to Sligo, the space included between those lines, which would occupy about one-fourth part of the entire superficial extent of Ireland, would contain about six-sevenths of the bogs in the island, exclusive of mere mountain-bogs, and bogs of no greater extent than 800 English acres. This district resembles in form a broad belt drawn from east to west across the centre of Ireland, having its narrowest end nearest to Dublin, and gradually extending its breadth as it approaches the western ocean. This great division is traversed by the river Shannon from north to south, which thus divides the great system of bogs into two parts. Of these, the division to the west of the river contains more than double the extent of bogs in the eastern division, so that if we suppose the whole of the bogs of Ireland (excicusive of mere mountain-bogs, and of bogs of less extent than 800 acres) to be divided into twenty parts, twelve of these parts will be found in the western division, and five parts in the eastern division of the district already described, while of the remaining three parts, two are to the south and one to the north of that district.