84 MR. GAEDIN^ER AXD PROF. REYNOLDS ON THE [Feb. igiZ^ 



(1) The Basal Conglomerate. 



The oldest Silurian rock is a coarse conglomerate, ^vhich is very 

 impersistently exposed. It crops out at several points when it 

 occurs in juxtaposition to specially hard rocks, such as the coarse 

 porphyrite and the dolerite dyke a third of a mile south-east 

 of Lough ATweelaun ; but the exposures are relatively few, and 

 the conglomerate frequeutly gives rise to a narrow tract of smooth 

 grass between the rugged outcrop of the breccias on the north, and 

 of the coarse porphyrite or lime-bostonite on the south. The best 

 locality to observe the conglomerate is in the neighbourhood of the 

 dolerite dyke just mentioned, and for about a quarter of a mile to 

 the east thereof. In the immediate neighbourhood of the dyke the 

 conglomerate is seen in close relationship to tlie coarse Areuig 

 breccia, and at one point seems to dip below it; the explanation is 

 probably that here the upturned base of the conglomerate rests upon 

 a very uneven surface of breccia. The pebbles of the conglomerate, 

 which are thoroughly well rounded, may reach a length of 10 inches, 

 and consist chiefly of pink quartzire. but include also granite, 

 felsite, quartz, and chert. 



(2) The Ked Sandstone. 



This is a somewhat current-bedded sandstone, very uniform in 

 character, and with its component quartz-grains cemented together 

 by ferric oxide. It is exposed all along the southern slopes of the 

 Knock Kilbride ridge from near Finny Chapel to the eastern 

 slopes of Knockn amuck. With the exception of an ill-preserved 

 coral, no fossils have been found in it. It occasionally becomes 

 conglomeratic, and may then include well-rounded pebbles of red 

 quartzite rather larger than a hen's egg. In rare cases it includes 

 small patches of red shale. Only at a single point, a spot north 

 of Kilmore, have we found it penetrated by one of the dolerite 

 dykes which are so abundant in some of the overlying rocks. The 

 maximum width of outcrop (about 300 yards) is met with east of 

 the summit of Knock Kilbride ; at Kilmore the width of outcrop is 

 reduced to about 100 yards. 



(3) The Annelid-Grits.i 



The red sandstones are overlain by yellowish or reddish-purple 

 grits, which very frequently have the bedding-planes covered by 

 numerous slight elevations rather less than a quarter of an inch 

 in diameter, which are seen in longitudinal section to be filled- 

 up tubes. The rock closely resembles the Serpulite-Grit of the 

 Durness area. The yellowish and purple grits pass up into a series 



^ The occurrence of these Annehd-Grits is mentioned in the Annual Eep. Geol. 

 Surv. for 1896 (1897) p. oO, where thev are stated to resemble the 'pipe-rocks' 

 in the Sutherland quartzite. The age of all these Silurian deposits is stated, 

 however, to be AYenlock. 



