604 Scientific Proceedings, Royal Dublin Society. 



gave excellent crops of wheat ; but since the change in the climate 

 which prevents the wheat from properly yielding and ripening, 

 and the consequent falling off in that crop, it is not much used. 



TYRONE. 



This, at the present time, is the premier sandstone country: 

 not, however, as regards quantity, but as to the quality to suit the 

 present market; and also as to variety, they being of different 

 colours, textures, and hardness, and belonging to various Geological 

 groups and sub-groups. 



To the northward, extending from near Omagh, north-eastward 

 into Londonderry, is the tract of metamorphic rocks, suggested by 

 Dr. Hinck as possibly of Laurentian age; but, as shown in the 

 "Introduction" (page 515), more probably the equivalents of the 

 Arenig, or even possibly of the Cambrian. In the vicinity of Pome- 

 roy, against these rocks is a small tract of rocks that possibly may 

 in part represent the Llandovery, which, as given in the Table of 

 Strata (Part i., page 204), are the Passage-beds between the Silu- 

 rian and the Ordovician ; these rocks, however, are evidently nearer 

 allied to the last than the first. 



On the southward of these strata is a considerable and wide 

 tract of Silurian, of the "Lower Old Eed Sandstone" type — the 

 eastern portion of the area already mentioned when describing 

 Fermanagh (page 560) ; and still further to the southward, in 

 places margining these rocks, is a narrow band of Lower Car- 

 boniferous Sandstone. 



North of the Tyrone Coal-field there is a tract of Calp Sand- 

 stone brought up by a fault, while there is a second south-west of 

 Dungannon (Dungannon Park). Farther south-westward, north- 

 east and south-east of Aughnacloy, are tracts of somewhat similar 

 rocks that have been classed among the Calp Sandstone; but it 

 should be pointed out that they are also more or less like the 

 rocks of the Fermanagh Series (Lower Coal-Measures) of the Slieve- 

 Beagh district, counties Fermanagh and Monaghan (page 561) ; 

 while in the neighbourhood of Aughnacloy they appear to join 

 into one another. It seems possible that in the latter neighbour- 

 hood the geology has not been properly worked out, and hereafter 

 (north of the Tyrone Coal-field), it will be found that the Coal- 



