VIL—Parrt I. ON THE NATURE AND ORIGIN OF THE BEDS OF 
CHERT IN THE UPPER CARBONIFEROUS LIMESTONE OF 
IRELAND. By Proressor EDWARD HULL, m.a., 4.z.8., Director of 
the Geological Survey of Ireland. 
Part Il. THE CHEMICAL COMPOSITION OF CHERT AND THE 
CHEMISTRY OF THE PROCESS BY WHICH IT IS FORMED. Ry 
EDWARD T. HARDMAN, rcs. 
PLATE III. 
[Read 17th December, 1877. ] 
PART I. 
Tue Carboniferous Limestone underlies the greater part of the central plain of 
Treland over which, however, it is generally concealed by beds of drift gravel, 
_ sand, and boulder clay which are spread over the lower grounds and the adjoining 
slopes of the hills. Along the south-east the limestone plain is bounded by the 
Granitic and Silurian rocks of the Dublin and Wicklow mountains; along the 
south and south-west by the ridges of Old Red Sandstone, which rise into the 
mountain ranges of Cork and Kerry ; along the west by the Metamorphic and 
Upper Silurian rocks, which form the mountains of Connemara and Mayo ; along 
the north-west by the Donegal Highlands, formed of similar strata ; and along the 
north-east by the uplands of Westmeath, and the mountainous region of Slieve 
Gullion, Carlingford, and Mourne, which is deeply indented by Carlingford Lough, 
and the channel of the Newry canal. Thus in nearly every direction the central 
plain is bounded by mountain ranges; but at rare intervals the limestone forms 
the marginal coast-line of the country, as along the shores of Dundalk, Dublin, 
Galway, Sligo, and Donegal Bays. 
Although generally occupying the plains, the limestone towards the north-west 
in the counties of Leitrim, Fermanagh and Sligo, rises into terraced hills of con- 
siderable elevation bounded by mural escarpments, and flanked by grassy or 
wooded slopes ; while in thecounty Clare, in the Barony of Burren, the formation rises 
into scarped terraced hills, bare (except for scanty herbage) from the base to the 
summit, each successive bed cropping out, tier above tier, and ending off in mural 
scars; thus presenting features somewhat similar to those of the “Scar Lime- 
stone,” of North Lancashire, Cumberland, and Yorkshire. 
Perhaps the most remarkable physical features of the Carboniferous jimestone 
districts of Ireland are the innumerable lakes with which its surface is studded, 
particularly over the central and northern portions of its range. In certain districts 
of Sligo, Fermanagh, Roscommon, Longford, Cavan, and Westmeath, lakes and 
0 
