12 
GEOLOGY OF THE FIRST DISTRICT. 
Notwithstanding this heavy tax upon our farmers for the importation of a mineral manure, 
they cheerfully pay it, because they are amply remunerated by the increased productiveness 
of their lands. The use of marl may prevent a large portion of this outlay; and it is sin¬ 
cerely hoped that our intelligent farmers will make the experiment of the marl, which is so 
abundant, and which has been accumulating during successive ages of time, by the growth 
and decay of myriads of animated beings, with a view to the final benefit of man. 
The term marl, in its strict mineralogical sense, means an argillaceous carbonate of lime ; 
but by general usage, marl is an earthy mineral substance, which, by being spread upon the 
soil, renders it more fertile. The marl which we have been describing, is a fresh-water shell- 
marl. The marls of New-Jersey, and the States south of it, are various in composition. 
Some are calcareous, and others are composed of green sandy grains, whose chemical com¬ 
position is a potash-silicate of iron. The marls of these States are marine depositions, and 
contain an abundance of the remains of marine animals. The fresh-water shell-marl of New- 
York will not yield to any other in its fertilizing effects, unless to the green marls of New- 
Jersey and Maryland. If it be judiciously employed, it will return millions to the pockets of 
our farmers. The argillaceous marls will be discussed in another place. 
Marsh Alluvions. 
Peat. This alluvion is the result of vegetable decomposition. It varies in its aspect: the 
best quality is a soft, unctuous, tremulous mud, when wet; but when dry, is so compact as 
to receive a slight polish. When heated, it burns with flame and bituminous odor. Lig¬ 
neous, fibrous, and compact peat are the principal varieties : The two former are of compara¬ 
tively little value ; the latter is extensively used in France and Ireland, and is considered a 
valuable fuel. It is used not only for domestic purposes, but also in burning lime, bricks, 
and pottery. In cold climates it is formed in moist ground and shallow ponds, wherever there 
is an accumulation of vegetable matter. Decayed trees form a light, soft, spongy mass, called 
ligneous peat. From decomposed grasses and seeds, a fibrous peat is formed, which is light 
and spongy several feet below the surface, but at a greater depth it may be of a good quality 
for fuel. Small aquatic plants, and mosses, such as the Sphagnum palustre, produce peat, 
which at a moderate depth is compact, without fibres, uniform in its texture, and of good 
quality. Many of the swamps or marshes where this combustible abounds, are overgrown 
with bushes and trees ; but those not so overgrown are covered generally with moss and cran¬ 
berry vines. The latter variety of peat bogs trembles under the foot. 
Peat abounds in many parts of the district; in fact there are few marshes that do not con¬ 
tain it. The best peat lies at the depth of three or four feet below the surface ; as that above 
often contains vegetable fibres of partially decayed plants, and is inferior in quality to the 
compact, black or brown tremulous mud that lies below. Ligneous peat, or that derived from 
decayed wood, is as common as the other, but is inferior in quality. It is found in almost all 
low grounds, and frequently contains the trunks and branches of cedar and other kinds of 
wood of great durability, which have undergone little change. 
