24 



GEOLOGY. 



KiNAHAN, G. H. Glacialoid or Rearranged Drift. Geol. Mag. dec. 2, 

 vol. i. pp. 111-117, 168-174. 



There have been four marked changes of level in Ireland since the 

 great Glacial period. The oldest is that of the Eskar Sea, or the 300- 

 feet sea-beach ; the second is marked by the 100-feet beach ; the third 

 by the 25-feet beach ; at the fourth period the land was at least 30 feet 

 higher than now. The subsequent depression, by which it was brought 

 to its present level, appears to be still in progress in certain places. 

 The accumulations of the three periods of depression are very similar. 

 The fossils have hitherto been grouped together ; but the author thinks 

 that, when worked out, those from different beds will be found to 

 differ. 



It has been supposed that there has been in Ireland a later Glacial 

 period, the Boulder Clay of which overlies the gravelly and other accu- 

 mulations just noted. The author thinks that this is not the case, and 

 regards the supposed Boulder Clay as a " glacialoid or rearranged drift." 

 One peculiarity of this drift is that the stones are frequently set on 

 end or arranged obliquely. Illustrations are given of how marine 

 erosion is now rearranging Boulder Clay on the west coast of Ireland ; 

 a similar action is supposed to have formerly occurred in Wicklow and 

 Wexford. Meteoric erosion also produces rearranged drift. 



During the eskar-sea period small local glaciers seem to have ex- 

 isted, which sent down their detritus over the shelly drifts ; but these 

 deposits are unimportant. Reference is made to the submarine forests, 

 and the proof that these are really due to depression. Postglacial 

 faults affecting the drift are frequently mentioned. W. T. 



. Geology of West Galway and S.W. Mayo, Ireland. Geol. 



Mag. dec. 2, vol. i. pp. 453-462 (woodcut). 



This paper is an epitome of one read at the British Association, 1874, 

 which gave an account of the progress of the Geological Survey during 

 the past seven years. The newest rock of the district is Carboniferous 

 Limestone, which extends in a curved line from Clew Bay to Bantry 

 Bay : there are small outliers of the LoAver Carboniferous rocks (sand- 

 stones, conglomerates, &c.) ; but these are feebly developed. The next 

 rocks, in descending order, are Upper Silurian ; of these there are two 

 distinct types ; .and local names are given to the subdivisions of each. 

 Both series contain interbedded felstones, and both rest unconformably 

 on rocks which are more or less altered. ,The metamorphism of the 

 rocks underlying the south-western area is often great,' some of them 

 having lost all traces of sedimentary character and being changed into 

 granite. The older rocks of the north-eastern area are less altered ; 

 fossils have been discovered in them -which prove that the " Doolough 

 beds " are of Lower Silurian* or Cambro-Silurian agg. It is believed 

 that . the highly altered rocks are of the same age, and" that they lie in 

 a great undulatory anticlinal curve which- rises towards the west and 

 exposes the lowest beds near the Atlantic. Sections of these- beds are 

 given. • . . 



It is evident that the granite is Hhe product and not the cause of 



