HOLGATE : CARBONIFEROUS STRATA OF LEEDS. 
11 
contain a large quantity of salt in solution, as do those immediately 
above the Beeston Bed Coal (See Tables Nos. 1 and 45.) 
Seat Earths. — These underlie each seam of coal however thin 
it may be, and are generally about 2 feet to 3 feet in thickness, from 
which we gather that this was the distance to which the coal mea- 
sure trees rooted. Like the trees of the present day those of the 
coal measures contrived to exist upon different kinds of soil whatever 
their preferences might be, and we find some rooting in mud as in 
that beneath the Beeston Bed (Table No. 40.) Others in loamy sand 
(see Table No. 18) as is the Black Bei Seat Earth, and others 'No. 
27) again in a micacious bind. In the Better Bed Seat Earth (No. 2) 
which is the fireclay for which Leeds is celebrated, the roots com- 
pletely destroyed all stratification, and made a soil just as trees do 
at the present day. In some, however, this has not taken place, and 
though the roots and rootlets are numerous we can distinctly see 
what the original deposit was like (See Table No. 27). In this case 
we find a micacious and bituminous bind. 
On examination we are struck with the fact that the thickness 
of the coal seams do not appear to bear any proportion to the depth 
of, or the quantity of roots in the seat earth ; a seam of coal 2 in. in 
thickness has as great a depth of seat earth and often as many roots 
as a coal seam having a thickness of some feet. If, however, we 
examine the overlying bed we shall see the reason of this, and shall 
find it to be for some feet in height, a shale, very black and bitu- 
minous. We shall also probably find stems of trees standing up in 
it. If we burn this shale it will give out a considerable amount of 
heat, and will lose a great deal of its weight, sometimes as much as 
two-thirds. From this we realise that the land was sinking at a 
greater rate than the trees and plants were growing, and that a coal 
seam does not represent the total amount of growth, but only that 
part of it which is made up entirely, or very nearly so, of vegetable 
matter. The trees and plants stood and grew for a long time after 
this, during which time mud was being brought down by streams 
and deposited in the spaces intervening between the plants. The 
time when the forest was quite destroyed is marked by a difference in 
the colour and in the nature of the deposits. The strata containing 
