172 Reviews — Trof. HulVs Physical Geologij of Ireland. 



sheet, as supposed to be proved by the scorings, etc., would be that line of least 

 resistance. A large mass of details of these scorings is given, filling more than 

 twenty pages — but these the student must consult tor himself. The thickness of the 

 great ice-sheet is held to have been at least 1000 feet, probably much more. 



The existence of local centres for glaciers towards the close of the glacial period, 

 after the submergence of the plains and the general re-emergence of the land again, 

 is then noted and some details given ; and the volume then concludes with a very 

 brief chapter " connecting the pre-human with the present age," a chapter which in 

 future editions we hope to see vastly extended. 



In reviewing the author's conclusions as a whole, there are only 

 a few points which appear to call for any special notice. One of 

 these is the much greater prominence which Mr. Hull has given 

 to the agenc}'^ of chemical solution, in the production of physical 

 results, than has been generally acceded to it. In a country where 

 limestone originally formed such a very lai'ge portion of the exposed 

 surface, it was only natural to find evidence on a great scale of this 

 action, and we gladly direct attention to the valuable observations 

 of the author on this point. In another direction also, that is, in 

 the fuller application of the effects of terrestrial disturbances as 

 causes of the present physical features of the country, we think the 

 author's views worthy of commendation. There has been of late 

 years too great a tendency to push to extremes the application of 

 some pet theories, till almost the very existence of other forces has 

 been ignored — and we are glad, therefore, to see the influence of 

 faults, and of deepseated disturbances, again appealed to, and 

 restored to its legitimate position in the sequence of formative causes. 

 The wide application of ice forces in their varied exhibition was of 

 course to be expected. The pages of this journal for years have 

 been so filled with valuable and detailed contributions to these 

 inquiries, that our readers are fully prepared to admit the importance 

 of this branch of geological research, and to accept many of the 

 conclusions which have been adopted. But, at the same time, the 

 very nature of many of these contributions to which we have re- 

 ferred suggests to every sound thinker, as we believe, the necessity 

 for great caution and watchfulness before admitting any new hypo- 

 thesis, however boldly or dogmatically it may be propounded, either 

 as a speculation, or possibly, even, as a fact; for there are many cases 

 in which this, too, has been done. In the analysis of the author's 

 views which we gave above, we have endeavoured to state them 

 with clearness and sufficient fullness to make them intelligible, pre- 

 ferring to leave them for the most part as the opinions of the writer 

 only, and not to discuss them as geological views or doctrines. 

 But we would not be justified in altogether passing over in this 

 way some of these views. With reference to the " General Glacia- 

 tion of Ireland," a conclusion worked out by the Eev. M. Close, as 

 to the axis or origin of motion of the ice-sheet over the island at 

 the earlier part of the great glacial period, is unhesitatingly adopted 

 by our author ; and he proceeds at once to propound — and in terms 

 which lead his reader to suppose that the whole thing was obvious 

 to the smallest consideration — a solution of this anomaly. He 

 supposes that snow and ice were heaped up over a belt of low 

 ground extending more than 100 miles in length, and, say, ten in 



