258 
Mr. Weaver on the 
of the field we may frequently remark an abundance of finely dis- 
seminated particles of iron pyrites ; to which, and the distribution 
of carbon and hydrogen in the composition of these rocks, we may 
in part ascribe the peculiarity and efficacy of the Lucan mineral 
waters, *3 well as of those of Golden bridge, near Dublin. 
§ 158. Some very interesting relations of the limestone tract 
are observable on those parts of the coast of the county of Dublin,, 
which we have not yet touched upon ; and of which I have 
already mentioned (§ 120.) that it was my intention to give a full 
description ; to which I now proceed. 
The line of demarcation between the floetz limestone and the 
transition rocks, which occupy the north-eastern part of the coast, 
passe* cm the west by Knock, between Balruddery and the Man of 
War, whence it follows an inclined line to the south of Skerries. 
Ac 13a! cumin it is associated with slate clay and lydian stone, and 
in Baldungan hill the principal constituents are lydian stone and 
flinty sLte ; these rocks dipping gently to the south-east. But at 
Malvertbtown and Hacketstown, which lie nearer to the coast,, 
the limestone is remarkably pure, and free from interstratified 
aulxstaQces, presenting in the quarry at the former place continuous 
strata from three to five feet thick, dipping 14° toward the south- 
east, which have been opened to the depth of fifty feet. This 
quarry furnished the cut-stone, of which Balbriggan church and 
tower are principally constructed. 
§ 159. The strand for about a mile to the south of Skerries: 
forms a curved sandy beach directed to the south-east, and lined in 
the southern part with a high bank of alluvial soil ; beneath 
which, at the extremity, a sheet of bluish grey limestone 
presents itself, spreading out to the north-east, and dipping: 
15° in that direction. It occupies the coast to the southward for 
