i7G Dr. BeRGer on the Geological Features 



In Carlntogher and Cragnashcack the chalk appears to be want- 

 ing, and the basalt to repose immediately on the sandstone ; but in 

 the insulated mass of secondary strata which cap the primitive mass 

 of Slieve Gallion (on the south of the great valley of denudation, 

 through which the Mayola flows) the chalk again appears under- 

 neath the basalt, and there attains its greatest elevation, being 

 quarried at the considerable height of 1460 feet above the level of 

 the sea, the deposit is however thin and the strata much split. 



On the east of Slieve Gallion is a valley about three miles in 

 breadth, occupied chiefly by red sand and marie, and succeeded 

 near Moneymore by a ridge of elevated ground, exhibiting chalk, 

 rising over the sandstone and surmounted by basalt ; this ridge 

 rises from Lough Neagh. At Ruskey it is but little raised above 

 the level of that lake ; it ranges in a direction towards the north, 

 passing a little to the west of Magherafelt, a continuation of it 

 may be traced to the east of the insulated primitive district of 

 Coolcoscrahan, thence bending round the source of the Kelvin, and 

 joining the lofty chain before described near Ballyness. The west- 

 ern escarpment of this ridge may be considered as limiting in that 

 direction the great basaltic area, Benbradagh, Cragnashoack and 

 Slieve Gallion, which lie without the boundary so assumed, form-, 

 ing insulated and outlying masses, separated from the principal and 

 continuous basaltic region by vallies of denudation. 



The elevation of this ridge does not appear to be very consider- 

 able ; it seems probable that the mulattoe will be found underlying 

 the chalk in this ridge as it does in the hills with which it is 

 connected from Ballyness to Benyavenagh. 



The south western limit of the area of chalk would be determined 

 by a line from Moneymore to Magheralin, this passes diagonally across 

 Lough Neagh, the strata which occur along it are of course concealed 



