I873-] Geology. 425 



be restricted to the Upper Silurian of Sir Roderick, whilst the term Siluro- 

 Cambrian might be applied to the Lower Silurian rocks. 



Capt. F. W. Hutton has communicated to the Geological Society a summary 

 of the Tertiary formations of New Zealand, classifying them as follows: — 



Pleistocene. 



p] . J Newer Pliocene, or Whanganui group. 



f Jiocene. -j 0Mer Pliocene> or Lignite group. 



Miocene I U PP er > or Arvatere group. 

 Miocene. j Lower) or Kanieri group. 



Oli^ocene - f U PP er ' or Hawke's Bay group. 

 v & { Lower, or Waitewata group. 



Eocene I U PP er > or Ototara group. 



(Lower, or Brown Coal group. 



Professor Hitchcock gives in the " Geological Magazine" a notice of the 

 precise areas occupied by workable beds of coal in the United States, and he 

 estimates the total to amount to 230,659 acres. This refers only to the coal 

 of Carboniferous age, and excludes other beds of commercial value, which 

 occur in the Triassic strata of Virginia, and in the Cretaceous rocks of the 

 territories west of the Missouri River, in California, Alaska, &c. 



Glacial Geology. — Mr. J. F. Campbell, the well-known author of" Frost and 

 Fire," recently communicated to the Geological Society of London a memoir 

 on the glaciation of Ireland. He stated that almost the entire surface of the 

 country consists of glaciated rocks more or less weathered. The polished 

 surfaces are covered in low grounds with drift — unstratified boulder clay being 

 next to the rock, and above it sands and gravels and peat-bogs. The probable 

 dimensions of the ice-engines which work on the surface of Ireland were shown 

 by comparison of glaciers in Iceland, Norway, and elsewhere, with the Irish 

 marks, which indicate ice of equal size. Horizontal grooves at 2000 feet 

 above the sea were instanced as proving ice more than 2000 feet thick, which 

 moved over Ireland into the Atlantic in a south-westerly direction. It was 

 shown that the ice at its maximum probably extended from the Polar Basin to 

 Cape Clear. Mr. Campbell concluded that the later denudation of Ireland 

 was due to glacial and marine action, and that rivers and sub-aerial denudation 

 have done little to obliterate the tool-marks of ice and the sea since the end 

 of the last of a series of Glacial periods. 



Origin of Lakes. — The glacial origin of rock-basins occupied by lakes, first 

 promulgated by Professor Ramsay, has received the attention and corroboration 

 of several American geologists. The theory was, however, combated by the 

 Duke of Argyll in his recent Presidential address to the Geological Society of 

 London, wherein he discussed the phenomena of denudation, referring 

 especially to the influence of subterranean and other movements of the crust 

 of the earth upon the denudation of its surface, and disputing the greatness of 

 the denuding effects of glacial action. 



The Rev. T. G. Bonney has likewise discussed the theory of the erosion of 

 lake-basins by glaciers, testing it by the Lakes of Salzkammergut, in the 

 North-Eastern Alps. He considered a far more probable explanation to be, 

 that the greater lake-basins were parts of ordinary valleys, excavated by rain 

 and rivers, the beds of which had undergone disturbances after the valley had 

 assumed approximately its present contour. He showed that the lakes were 

 in most cases maintained at their present level by drift ; and that, while in 

 a region so subject to slight disturbances as the Alps positive evidence for 

 his theory would be almost impossible to obtain, no lake offered any against it, 

 and one, the Konigsee, was very favourable to it. 



Signor Gastaldi, however, in describing the valley of the Lanzo and other 

 Alpine valleys, pointed to the occurrence of large cirques at heights between 

 5000 and 10,000 feet. He noticed the various rocks in which these cirques 

 were cut, and expressed his opinion that they are the beds formerly occupied by 

 glaciers, the power of which to excavate even comparatively hard rocks, such 

 as felspathic> amphibolite- and chlorite-schists, he considered to be proved. 



