HOLGATE : CARBONIFEROUS STRATA OF LEEDS. 
15 
A noticeable feature in some of these strata is the way in which 
casts and ironstone nodules have been acted upon by lateral 
pressure. They have evidently been formed before the land was 
elevated, and the pressure has caused them to slide among the 
shales or sandstone and has caused a foliation to take place round 
the hard object. It has in fact produced a cleavage concentric with 
the tree or nodule of ironstone (See Table No. 26). 
I would also point out particularly the rapid changes which 
took place in the beds numbered 47 to 51. In this case the animals, 
which would no doubt have gone on living and dying gradually as 
they have done in the other black shales, were brought to an un- 
timely end, probably through the drying up of the arm of water in 
which they lived ; this is the only way in which we can explain why 
there are so many fish remains and remains of anthracosia in this 
thickness of four inches. The shale is hardened, not by the deposition 
of carbonate of iron, but by the permeation of the oily matter from 
the animals. The corners adjacent to the two planes of cleavage are 
rounded as though water had taken away some of the matter in its 
passage along these planes. The surface clays have long ago been 
used for brickmaking, by surface clays I mean the original covering 
of drift, which consisted of shales and pebbles. These had been 
washed in water as they were being deposited, consequently had had 
all the hydro-carbonaceous matter washed out of them. In order to 
make bricks from this material it was necessary to give it plasticity 
by hydrating it, and for this purpose it was kept in a wet state for 
weeks, and repeatedly turned over. 
N.B.— In the following Table of the Strata, No. 1 is the lowest 
in the sections, and each succeeding number represents the 
strata in ascending order : — 
