to
moist situations, where the temperature is low, and where vegetables may
decompose without putrefying. It may consist of any of the numerous
plants which are capable of growing in such _stations_; but a species of
moss (_Sphagnum_) constitutes a considerable part of the peat found in
marshes of the north of Europe; this plant having the property of
throwing up new shoots in its upper part, while its lower extremities
are decaying.[1003] Reeds, rushes, and other aquatic plants may usually
be traced in peat; and their organization is often so entire that there
is no difficulty in discriminating the distinct species.

_Analysis of peat._--In general, says Sir H. Davy, one hundred parts of
dry peat contain from sixty to ninety-nine parts of matter destructible
by fire; and the residuum consists of earths usually of the same kind as
the substratum of clay, marl, gravel, or rock, on which they are found,
together with oxide of iron. "The peat of the chalk counties of
England," observes the same writer, "contains much gypsum: but I have
found very little in any specimens from Ireland or Scotland, and in
general these peats contain very little saline matter."[1004] From the
researches of Dr. MacCulloch, it appears that peat is intermediate
between simple vegetable matter and lignite, the conversion of peat to
lignite being gradual, and being brought about by a prolonged action of
water.[1005]

_Peat abundant in cold and humid climates._--Peat is sometimes formed on
a declivity in mountainous regions, where there is much moisture; but in
such situations it rarely, if ever, exceeds four feet in thickness. In
bogs, and in low grounds into which alluvial peat is drifted, it is
found forty feet thick, and upwards; but in such cases it generally owes
one half of its volume to the water which it contains. It has seldom, if
ever, been discovered within the tropics; and it rarely occurs in the
valleys, even in the south of France and Spain. It abounds more and
more, in proportion as we advance farther from the equator, and becomes
not only more frequent but more inflammable in northern latitudes.[1006]

The same phenomenon is repeated in the southern hemisphere. No peat is
found in Brazil, nor even in the swampy parts of the country drained by
the La Plata on the east side of South America, or in the island of
Chiloe on the west; yet when we reach the 45th degree of latitude and
examine the Chonos Archipelago or the Falkland Island