15 6 The Rev. Maxwell H. Close, 



Upper Boulder Clay. — Over the generally well- washed and 

 stratified Middle sands and gravels may sometimes be seen a 

 nearly, occasionally quite, unstratified deposit, which we may 

 call the Upper Boulder Clay, without implying thereby that it 

 has been formed in the same way as the Lower Boulder Clay. 

 It is of a looser, more earthy material, and may contain far- 

 travelled stones. But as the nature of this deposit, if it be 

 really a separate one, is obscure, and there is considerable differ- 

 ence of opinion thereanent, and as entering into controversy is 

 outside our present business, we shall pass on to the next. 



Eskers. — These seem to be the latest of these drift accumula- 

 tions. We shall not now go into the difficult and vexed question 

 of their mode of formation. They must be as old as the time of 

 floating ice, as they sometimes have very large transported 

 blocks lying upon them, just as the level drift often has. It is 

 sometimes evident that these have not been brought out by 

 denudation, but that they have been dropped on the esker by 

 some agency that did not interfere with the gravel and sand 

 already there ; and the only agency that can be suggested is 

 floating ice. The eskers consist of thoroughly well washed and 

 generally stratified materials. Shell fragments have been found 

 in them, but only in one or two instances. As their name implies, 

 they are generally in the form of ridges, though they are often 

 but more or less well-defined irregular mounds. There is a good 

 specimen of a ridge esker at Greenhills, a couple of miles W. of 

 Rathfarnham. Its whole length is nearly three miles, and its 

 height from thirty-five to sixty feet. A road runs along the 

 crest of its southern portion, where it is narrower and well-defined, 

 for a length of two and a quarter miles. There is also a ridge 

 esker at a place thence called Esker, on the S. side of the Liffey, 

 six miles W. of Dublin, and there are irregular esker mounds in 

 Stillorgan Park and elsewhere. 



Local Glaciation. — This is doubtless the proper place in which 

 to mention the glacial moraines which are to be found among the 

 hills in the neighbourhood of Dublin. It is most probable that 

 those moraines were finally left by the ice, as we now see them, 

 about the time of the formation of the eskers or shortly after that. 

 Each of the two Loughs Bray (12 miles S. by W. from Dublin) 

 occupies its own division of a laterally double hollow on the N.E. 

 side of Kippure Mountain (granite, 2,473 feet above the sea). The 



