604 MESSES. S. H. REYNOLDS AND C. I. GARDINER [ISOV. 1 896, 



The general arrangement of the igneous rocks of Grange and 

 Allen Hills may be shown in the fV lowing synopsis : — 



At the top : 



Grange. Allen. 



5. Andesite forming a small patch 5. Variable rocks, the best-marked 

 overlying the porphyritic basalt being the hypersthene-augite- 



towards the south-western end andesite having a groundmass 



of Grange Hill. crowded with square or rect- 



angular felspars. 



4. Porphyritic basalt, with large 4. Porphyritic basalt, with large 

 crystals of labradorite. crystals of labradorite. 



3. Basalt, sometimes amygdaloidal, 3. Basalt, sometimes amj-gdaloidal, 

 sometimes with large fresh sometimes with large fresh 



augites. augites. Its colour is red or 



dark green, and it occurs along 

 the south-eastern face of the hill. 



2. Augite-andesite, often showing 2. Wot seen. 

 good fluxion-structure. 



1. Band of ash seen along the 1. Not seen, 

 northern foot ; below it, at two 

 points, lava is visible. 



IX. General Conclusion and Summary. 



All the rocks exposed in the Kildare inlier are either of Silurian 

 or of Ordovician nge. Those tying west of the fault which runs 

 between Dunmurry Hill and the Chair are probably of Silurian age, 

 while the fossiliferous beds east of the fault show that we are here 

 dealing with rocks of Ordovician a°;e. With the doubtful exception 

 of one exposure of grit, all the beds east of the fault are referable 

 to the Middle Bala. 



Grange Hill and the Hill of Allen are mainly composed of con- 

 temporaneous igneous rocks, all the lavas being of the nature of 

 basalts or andesites. We found no clear evidence of the occurrence of 

 intrusive rocks anywhere in the inlier. The igneous rocks of Grange 

 Hill are overlain and underlain by sedimentary deposits containing 

 Middle Bala fossils. With regard to the age of those of the Hill 

 of Allen, we have no definite evidence ; but their resemblance to 

 those of Grange Hill is so great that we feel justified in regarding 

 them, and so the whole of the igneous rocks of the area, as of the 

 age of Sedgwick's Middle Bala. 



We wish to express our best thanks for kind help to Messrs. Marr 

 and Harker. and especially to Mr. W. W. Watts and Mr. Cowper 

 Reed ; also to Prof. Sollas and various members of the Irish Geological 

 Survey, for the privilege of referring to the Survey Maps at Dublin. 

 Also to Mr. P. Doyle, of the Chair Earm, Kildare, for his uniform 

 courtesy. 



