175 
We will next consider Peat, or Turf, as a fuel. Peat 
consists of decayed plants accumulated through a number 
of years, and compressed into a compact form by the weight 
of successive layers annually superimposed. When on a 
retentive soil, the flatness of the land or temporary ob- 
structions prevent the outlet, and cause the consequent 
stagnation, of water, the area will soon be overgrown by 
water plants of all descriptions, as the sedges, rushes, algae, 
mosses, &c. A species of moss, called spagnum, having 
the property of throwing up new shoots on its upper part, 
while its lower extremities are decaying, is the principal 
plant found in such situations. These plants, during the 
winter, die and fall to the ground, making room for another 
crop in the ensuing spring. The constant succession of 
this process produces a vast accumulation of decaying 
organic matter, which evolving carburetted hydrogen, 
( C 2 H 4) carbonic acid ( co 2 ) 5 and defiant gas (C 4 H 4 ) ? 
and other noxious gases, and taking up oxygen from the 
surrounding water and soil, assumes the form familiar to 
us by the name of peat. The superposition of Kimmeridge 
upon Oxford clay, without an intervening porous stra- 
tum, is the most favourable locality for its formation, and 
is well exemplified in Lincolnshire, where such an order 
of stratification actually exists. The nature of peat varies 
with its geological a^e, and may be divided into recent 
peat, exhibiting still the roots and stems of the plants 
from which it was formed, very porous, and of a light 
fibrous texture ; and the older peat, reposing below this, in 
which the fibrous merges into an earthy texture, and of 
which the weight of a cubic foot varies from 50 to 80 lbs., 
while the former weighs only 4. The composition of 
peat varies extremely with its age, density, and the locality 
from which it is obtained. The general result of its analysis 
gives, carbon 57, hydrogen 6, oxygen 32, and 5 of ash. The 
VOL. III. m 2 
