Notes on Glacial Deposits in Ireland. 327 



From a clean face in the lower portion of the deposit of 



Boulder-clay, we gathered 129 stones and pebbles at random, 



which, when examined, yielded the following percentages : — 



Carboniferous limestone, - - - 38' 2 



Basalt, - - - - - - 15*8 



Carboniferous sandstone, - - - 15*0 



Hard chalk, - - - - - 5'o 



Slate, - - - - - . 5-0 



White quartzite, - - - • Z'^i 



Felstone, - - - - - Tt'Z 



Black flint, - . . . _ 2*5 



Cambrian sandstone, " - - - - 2*5 



Cambrian slate, - - - - - 1*6 



Coal-measure shale, - - - - i*6 



Black micaceous grit, - - - - i'6 



Triassic sandstone, . - . . -8 



Epidiorite, . .... -8 



Granite, ------ -S 



Rhyolite, - - - - - -8 



Lignite, ------ -8 



White quartz, - - - - - -8 ' 



lOO'O 



It will be immediately observed that although the deposit 

 lies on granite, which extends in every direction for several 

 miles, this rock was only represented in the 129 pebbles by a 

 single specimen, w^hile more than half the total are derived 

 from the Carboniferous rocks. Still more remarkable is the 

 comparative abundance of basalts of precisely the same 

 character as those which are found in places in the north of 

 Ireland. But while this is certainly the nearest locality from 

 which these rocks can have been derived, it by no means 

 follows that they may not have come from points still further 

 north The northern origin of the basalts is in accord with 

 the occurrence of no less than 7*5 per cent, of Cretaceous rocks. 

 None of the other pebbles call for special remarks except one 

 of rhyolite agreeing in character with that of Forkill near 

 Dundalk, the nearest point fronr which it can have been 

 derived. 



In addition to collecting pebbles for per-centage purposes, 

 we paid special attention to the larger blocks. These occur 

 almost exclusively on the denuded surface of the Boulder-clay 

 at the base of the overlying gravels, and they present a very 

 interesting assemblage. Among numerous specimens of 

 riebeckite-beahng granophyre (Ailsa Craig rock) may be 

 mentioned one angular block measuring i' ;< 8" x 8". Its sur- 

 face was rough, and did not exhibit striation. Of the various 



