binnie: mesozoic rocks of the north-east coast of irelan'd. 61 
(1) Columnar basalt. 
(2) Ck}^ or lignite. 
(3) Flint gravel, overlying the chalk with grey flints. 
The workmen obtain stems of trees from the lignite, and the 
lignite contains 75.8 per cent, of volatile and combustible matter. 
Jukes says : — " How, if the basalt did not burn up the lignite, did it 
manage to redden the flints which underlie it ? " Again, he says that 
the dykes only harden the chalk for a few feet on either side ; the 
induration of the chalk is not due to the basalt. 
The chalk bears great evidence of denudation, (1) in the hollows 
which occur at the top, and (2) in the quantity of flints which fill 
these hollows, which indicate that they are the accumulation derived 
from a great deposit of chalk, which has been carried away by water. 
They have also a very variable thickness, the deposit being 100 feet 
thick at Whiteliead, and only a few feet at Colin Glen, while it is 
absent altogether in Woodburn river. At the base of the chalk there 
is a glauconite layer, indicating conditions like those existing when 
the Greensand was deposited. The chalk is covered generally with 
dendritic markings of Pyrolusite, it contains also some phosphate 
nodules, and curiously shaped flints called Paramoudras, similar to 
those found in England in the Belemnitella chalk. 
Barrois says that in microscopic structure and chemical com- 
position it is identical with that of England, The flints contain many 
minute organisms, sponge spicules, etc., forming a powder. These 
have been carefully examined by the Belfast Naturalists' Field Club. 
The chalk is obtained for lime-burning, the basement beds 
being the best, as the lime formed from them sets more rapidly. It 
splits too easily along the planes of bedding to be used as a building 
stone. The chalk is nearly constant along the whole line of coast, 
though the thickness varies immensely. Near Duugiven, and from 
thence to Down Hill, it is only 20 to 30 feet thick. In Colin Glen it 
is also very poorly developed. 
The chalk seems to have partaken of the same movements as 
the underlying beds down to the Paheozoic rocks, in fact the foldings 
all seem to have taken place in Tertiary times. 
Mr. Tate concludes that the Irish chalk represents a high stage in 
