1856.] 



HAUGHTON — GRANITES OF IRELAND. 



199 



which it is in all probability a continuation, as shown in the accom- 

 panying map of parts of Down and Armagh, fig. 2. It is composed 



Fig. 2. — Map of the Ulster Granites. 



^ ^,^"^1 Potash- Granite. 



Soda- Granite. 



Silurian Slate. 



Carboniferous 

 Limestone. 



of quartz, white feldspar, and green mica, and resembles in its phy- 

 sical and mineralogical character the granite at the base of Slieve na 

 glogh. This resemblance is not confined to its external character, 

 but exists as to its chemical composition, as is shown by the following 

 analysis of the average granite, near Wellington Inn. In the cutting 

 of the Belfast Junction Railway near this place, numerous trap-dykes 

 are seen penetrating the granite, and may be traced for a considerable 

 distance in the small quarries of the neighbourhood. 



Wellington Inn Granite. 

 Quarts, Orthoclase, Green Mica. 



Specific gravity =2'61 5. 



Per cent. Atoms. 



Silica 71-24 1-549 



Alumina 14*361 o*'^9l 



Peroxide of iron. . 3'36j ' * ' ' 



Lime 1-48^ 



Magnesia 0*64 [ ^ ^70 



Potash 4-09 f-' ""^^^ 



Soda 3'13j 



Loss by ignition. . 1*50 



99-80 

 If we assume, as in the discussion of the corresponding granite of 



VOL. XII. PART I. P 



