DEPOSITED IN WATER. 
19 
tions which result from that combination may be employed in de- 
termining the analogies and differences of the Irish, English, Scottish, 
and Belgian types. 
Throughout Wales and the greater part of England, as in the 
South of Yorkshire, the mountain limestone requires no subdivision into 
groups ; it is, in fact, one great calcareous mass, neither graduating into, 
nor alternating with, the coal deposits above ; nor much connected in 
this manner with the sandstones below. Over a great part of Ireland 
only one thick limestone group is seen, but in the vicinity of Enniskillen 
an upper portion appears. The triple division adopted for Derbyshire, 
by Mr. Farey, rests on no better principle than a geological accident. 
But the north of England exhibits a transition between the limestone 
and coal formations, which in all the district north of the Aire and the 
Ribble becomes extremely complicated. In Yorkshire are two prin- 
cipal types of the mountain limestone series, as expressed in the ac- 
companying diagram, both covered by the millstone grit group. 
Northern series. 
1000 feet thick, 
and complicated 
Lower limestone group 
ICS. 
f Limestone 
| Coal 
- Flagstone 
- 
Limestone 
Shale 
Partially 
divided by h 
_ shales, &c . ) 
Southern series. 
Upper limestone group f Black, lamina- 
comparatively thin, J ted limestone, 
and simple ( and shale 
Lower limestone group nearly undivided 
DISTRICTS IN WHICH THE SOUTHERN SERIES PREVAILS. 
If a straight line be drawn from Jervaux abbey on the Yore, 
through Kettlewell on the Wharfe, to Ryeloaf hill near Malham, and 
thence continued westward to Lancaster, it will divide the Yorkshire 
limestone tract into two parts, remarkably contrasted in the character 
of the limestones. In the northern districts the lower limestone 
rocks are covered by a thick and complicated series of limestone, flag- 
stone, shale, coal, &c. ; in the southern, all the terms of this series 
d 2 
