174 Revieivs — Prof. HuWs Physical Geology of Ireland. 



across the Glendalough valley by the glacier that descended the vale of Glendasan. 

 This moraine had originally pent up the waters of the lakes, and against its northern 

 flank the old terrace of gravel (described in another page) has been deposited. 

 Afterwards the river cut down its channel and lowered the level of the waters. In 

 this view Professor Eamsay concurs." 



Here the question naturally occurs — Is the Round Tower and are 

 the " Seven Churches " at Glendalough really built on a moraine, or 

 on a river terrace ? Nothing is more probable than that a terrace — 

 not however a river-terrace — should have been deposited against the 

 flank of a moraine damming up a lake. But this is not the point 

 here. If in so accessible, and so easily examined and well-marked 

 a locality as Glendalough, it required careful re-examination, and the 

 aid of Prof. Eamsay, to find out that the foundation of the Round 

 Tower was placed, not on a river-terrace, nor even on a terrace, but 

 on a moraine (the two being of totally different ages, and due 

 to totally different causes), we are compelled to think that there 

 must still hang a thick mist of doubt and uncertainty over very 

 many of the thousands of observations of glaciation phenomena 

 which have been recorded. Nor is it within the just limits of ex- 

 pectation to hope that we shall find every one as open to conviction, 

 and as ready to acknowledge error, as Prof. Hull has shown himself 

 to be. Until, however, these doubts be removed, we can have no 

 hwioledge of the facts — for, as the Stagyrite says, "knowledge is 

 the solution of doubts." 



We have felt the want ourselves, and, therefore, do not hesitate 

 to notice it, as it possibly may be supplied in future editions, of a 

 little more aid to the imagination of the reader, by appeals to his 

 eye. The general features and scenery of parts of Ireland are 

 familiar enough to many, but even of those who know such scenery 

 in detail, how few have realized the general character of the outline, 

 or its essential dependence on the structure of the rocks below. 

 Geologists will remember gratefully the vast aid which they derived 

 in framing a general conception of the S.E. of Ireland from the 

 admirable panoramic sketches of Weaver (Trans. Geol. Soc. Lend. 

 1st series, vol. v.). But we would refer to far more recent, and far 

 less costly, illustrations of this kind in the many valuable publica- 

 tions of the Geological Survey of the United States Territories 

 under Prof. Hayden. Some of these, though almost pure outline, 

 convey the most wonderfully clear and accurate idea of the structure 

 of the country represented, and of the intimate dependence of its 

 physical features on that structure. And if a few such general 

 outlines of the more marked centres of interest in Irish scenery 

 and Irish geology could be given, we have no hesitation in thinking 

 that the book would commend itself to a far wider circle of readers 

 than it is likely at present to command. 



The British Association meet in the capital of Ireland in the 

 coming autumn, and there is every prospect that a large concourse 

 of visitors will then be attracted in addition to the ordinary crowd 

 of visitors. The well-known and generally appreciated hospitalities 

 of Dublin, the loveliness of the scenery of the country, and the 



