1874. | Peat Bogs. 299 
plants growing on the surface collecting their inorganic food 
from the atmosphere, and after their decay to the collected 
mineral substances being continually carried downwards by 
the water percolating through the mass: in this way each 
lower portion becomes more impregnated than the parts 
above it, and when burnt its ash or residue is greater. 
The bogs on mountains are vastly different from those on 
the low lands. The latter usually grow on more or less Hat 
places, where the substratum is non-porous, on which they 
form extensive level plains, while in the mountainous districts 
bog may grow anywhere on the hill-tops, as well as in the 
valleys, and from the latter they creep up the slopes over 
porous and non-porous strata. They are generally of small 
depth as compared with the lowland bogs, as here the peat 
grows much more slowly and more densely. In typical 
mountain bogs the clearing, or partly living organic matter, 
rarely exceeds 12 inches in depth, and this les on brown 
turf, under which there may be black turf, but not always, as 
in some places the peat envelope is too thin to form the 
latter by compression. The difference between mountain 
and lowland peat is evidently due to the different rate of 
growth of the peat-producing plants in the respective posi- 
tions. In the low flat land the growth of the plants is more 
rapid than among or on the mountains; consequently while 
on the former a light spongy substance is accumulating, on 
the latter a heavy felt-like mass is being formed. Besides, 
in all mountainous distri¢ts portions of the peat are very 
much subject to denudation by rain, runlets, and wind, 
which carry particles of peat from one place to another, and, 
by depositing them on the surface of the growing peat, keep 
the surface even, and make the peat compact and firm. In 
this way, on the growing peat may be deposited a layer of 
derivate or sedimentary peat, which will afterwards become 
interstratified by a subsequent growth of the plants. In flat 
mountain bogs, and also in the lowland bogs, when the latter 
are situated at the base of a hill or along a river subject at 
times to extensive floods, layers of sand, gravel, silt, or the 
like, may be found in the peat, such foreign material having 
been deposited on the surface of the bog during freshets, 
while afterwards the peat grows over them. 
In coal-mining we find parts of seams absent; such defi- 
ciencies are called “ faults,” ‘‘ troubles,” ‘‘ horses,” &c., by 
the colliers, and the formations of these coal-less portions 
of a vein are explained by the study of some peat bogs; as 
we find the mass of the peat in some places denuded by the 
wind, and in others by a stream, which cut into it and break 
