1&23.~] the principal Mountain Clutins of Europe. 139 



Trap rocks (porphyry, greenstone, basalt, &c.) occur exten- 

 sively associated with and overlying the coal districts of Scotland. 



(C.) Ireland. 



We shall next proceed to Ireland, postponing the enumeration 

 for the present of the English coal districts ; because the former 

 country is more immediately connected in its geological relations 

 with Scotland. 



As we have already traced the primitive and transition chains- 

 from the south-west of Scotland to the north-east of Ireland, 

 the formations of the great central valley of Scotland here like- 

 wise intervene, and among them the coal measures, which may 

 be seen emerging from beneath the overlying basalt at Fairhead 

 on the north-east, and again just beyond the south-west of the 

 basaltic area at Coal Island and Duncannon ; but other parts of 

 Ireland present far more important coal districts. Indeed th« 

 island may generally be described (with the exception of the 

 north-east basaltic area) as being almost surrounded with a series 

 of primitive and transition groups, including a great central area 

 entirely occupied by the old red sandstone, carboniferous linie,. 

 and coal measures. The structure of these districts very closely 

 corresponds with the tracts of the same formation in England. 



The coal district already mentioned is termed by Mr. Griffiths 

 the. Ulster coal district. There are three other principal coal 

 fields. 



2. The Connaught coal district occupies an extensive tract, in 

 the centre of which Lough Allen is placed. 



3. The Leinster coal district is situated in the counties of 

 Kilkenny, Queen's county, and county of Carlow. It also 

 extends a short distance into the county of Tipperary, as far as 

 Killenaule. This is the principal carbonaceous coal district. 

 It is divided into three detached parts, separated from each 

 other by the carboniferous limestone, which not only enve- 

 lopes, but in continuation passes under, the whole of the coaL 

 district. 



4. The Munster coal district occupies a considerable portion 

 of the counties of Limerick and Kerry, and a large part of the 

 county of Cork. It is by much the most extensive in Ireland ; 

 but as yet there is not sufficient information respecting the num- 

 ber, extent, or thickness, of the beds of coal it may contain. 



(D.) England. 



The coal fields of England will, from geographical position,, 

 naturally fall under the following arrangement : 1 . The great 

 northern district, including all the coal fields north of Trent. 

 2. The central district, including Leicester, Warwick, Stafford, 

 and Shropshire. 3. The Western district, which may be subdi- 

 vided into North-western, including North Wales, and the South- 

 western, including South Wales, Gloucester, and Somersetshire. 



