In meadows and marshes, overflowed by the ocean tides, we have _salt-peat_, formed from Sea-weeds (_Algæ_,) Salt-wort (_Salicornia_,) and a great variety of marine or strand-plants. In its upper portions, salt-peat is coarsely fibrous from the grass roots, and dark-brown in color. At sufficient depth it is black and destitute of fibres. The fact that peat is fibrous in texture shows that it is of comparatively recent formation, or that the decomposition has been arrested before reaching its later stages. Fibrous peat is found near the surface, and as we dig down into a very deep bed we find almost invariably that the fibrous structure becomes less and less evident until at a certain depth it entirely disappears. It is not depth simply, but age or advancement in decomposition, which determines these differences of texture. The "ripest," most perfectly formed peat, that in which the peaty decomposition has reached its last stage,--which, in Germany, is termed _pitchy-peat_ or _fat peat_, (_Pechtorf_, _Specktorf_)--is dark-brown or black in color, and comparatively heavy and dense. When moist, it is firm, sticky and coherent almost like clay, may be cut and moulded to any shape. Dried, it becomes hard, and on a cut or burnished surface takes a luster like wax or pitch. In Holland, West Friesland, Holstein, Denmark and Pomerania, a so-called _mud-peat_ (_Schlammtorf_, also _Baggertorf_ and _Streichtorf_,) is "fished up" from the bottoms of ponds, as a black mud or paste, which, on drying, becomes hard and dense like the pitchy-peat. The two varieties of peat last named are those which are most prized as fuel in Europe. _Vitriol peat_ is peat of any kind impregnated with sulphate of iron (_copperas_,) and sulphate of alumina, (the astringent ingredient of alum.) _Swamp Muck._--In New England, the vegetable remains occurring in swamps, etc., are commonly called _Muck_. In proper English usage, muck is a general term for manure of any sort, and has no special application to the contents of bogs. With us, however, this meaning appears to be quite obsolete, though in our agricultural literature--formerly, more than now, it must be admitted,--the word as applied to the subject of our treatise, has been qualified as _Swamp Muck_. In Germany, peat of whatever character, is designated by the single word _Torf_; in France it is _Tourbe_, and of the same origin is the word _Turf_, applied to it in Great Britain. With us turf appears never to have had this signification.