KiXAHAX — On Granitic and other Ingenite Rocks. 127 



To the north and north-east, the gneissoid-granite seems to have 

 similar constituents to the typical rock ; but the mica and quartz, 

 "vrith part of the felspai', are arranged in leaves or plates, vrhile the 

 large crystals of felspar are generally arranged rudely parallel to the 

 layers, but not always, as they often cut across them ; schistoid-beds 

 also occiu- in. it. The foliation, irrespective of the dip of the original 

 rocks, is perpendicular, or nearly so ; but the strike seems always to 

 correspond with that of the stratifieation of the associated gneiss. 

 However, as the rock loses its granitic character, and becomes more 

 and more gneissose, the original dip of the rocks becomes apparent. 



Among the metamorphic derivate rocks of the barony of Ballyna- 

 hinch or Connemara, there are large and small tracts of granitoid- 

 gneiss, the rock being identical with the g-neissoid-gTanite, forming 

 the north and north-east limits of the great tract of Galway -type- 

 granite. These tracts always occur in, and naturally might be consi- 

 dered a portion of, the gneiss-series ; nevertheless, in some places the 

 rock loses all traces of foliation, and becomes a granite undistingiiish- 

 ble from the Galway-type-rock, the essentials, accessories, structure, 

 and aspect being identical. 



That these tracts of granitoid-gneiss, or gneissoid-granite, are 

 highly metamorphosed parts of the gneiss-series, and not accidental 

 intrusions of granite, to me seems proved, as the one rock not only 

 graduates into the other, but also in places schistoid layers will 

 ti^averse the gTanitic rock, these layers having a strike and dip agree- 

 ing with those of the stratification of the associated gneiss and schist. 

 Such changes in isolated portions seem due to portions of the derivate 

 rocks, on account of the materials composing them being more easily 

 changed than the associated strata. This is very conspicuous at 

 Forlorne Poiut, Co. Wexford, where beds of granite are found associated 

 and interstratified with beds of incipient micasyte, hornblendyte and 

 taleyte. 



The change from gneiss into granite is most remarkable in the con- 

 giomeritic and nodular rocks. As previously pointed out, all former 

 structure, except the strike of the stratification, is generally oblite- 

 rated in the granitoid-gneiss, the only exception apparently being, 

 that some of the blocks in congiomeritic gneiss, more or less modified, 

 may still appear. This, however, is not generally the case, for, as the 

 rocks become more and more g-neissic, the blocks usually become elon- 

 gated, with the foliation curling more or less round them, but subse- 

 quently the foliation becomes parallel in lines, the matrix having a fine 

 texture, while that of the blocks is coarse (Tig. 0, PI. 10) ; the boundary 

 between each being still apparent ; and as the change progresses, all 

 seem to differ very little in texture, or rather one merges so gradually 

 into the other, that there is no difference discernible, till eventually all, 

 or all conspicuous foliation, disappears, and the rock becomes a typical 

 granite. 



Associated with the tracts of hornblende-rock {inetamorpliosed tcliin- 

 stone and euryte) are smaller or larger masses of granite, similar to the 



