Reviews — Geology of Caithness. 279 



II.— The Geology of Caithness. By C. B. Crampton and R. G. 



Carruthers ; with contributions by John Horne, B. M. Peach, 



John S. Flett, and E. M. Anderson. Memoirs of the Geological 



Survey of Scotland (Sheets 110 and 116, with parts of 109, 115, 



and 117). pp. viii and 194. 1914. 



rpHE appearance of this memoir marks an important advance in our 



J_ knowledge of tbe geology of the north-east of Scotland. It 



deals mainly with the Caithness Flags and the strata associated with 



them, freshwater rocks of exceptional lithological character, and 



presenting problems of the greatest interest. Dr. Strahan tells us in 



his preface that the survey was long in progress, so long that as the 



services of many of those who took part in it were no longer available 



some re-examination of the area mapped by them became necessary, 



conditions unfavourable for uniformity and completeness, but they 



have not seriously affected the value of the work. 



In his introductory chapter Dr. Flett formally accepts the Middle 

 Old Bed Sandstone age of the Orcadian rocks, though there is 

 nothing in the evidence at present available, which is inconsistent 

 with an attribution of the unfossiliferous rocks below the 

 unconformity at the base of the Berriedale and Ellensgoe con- 

 glomerates to the Lower Old Bed Sandstone. Of especial interest 

 is the regular rhythm of sedimentation in the Caithness Flags, each 

 cycle having a thickness of from 35 to 65 feet. This recurrence is 

 considered to be the result of warping, but it seems more probable 

 that it is due to periodic variations in meteorological conditions. It 

 is a great misfortune that the untimely death of Dr. Traquair has left 

 the evidence for the zoning of these rocks by means of their fish- 

 remains in an incomplete state. There can be no doubt that the 

 special fauna of the Johno' Groat's Beds is of true zonal significance, 

 but it is by no means clear how far this is the case with other 

 variations in the species of fish which are present. Full details are 

 given of the important discovery of the Achanarras fauna at Niandt 

 on the east coast. It is difficult, however, to correlate the account of 

 the beds at Achanarras with that given by Dr. Traquair, who saw 

 them under more favourable circumstances. This account might well 

 have been reproduced, as the Proceedings of the Royal Physical 

 Society of Edinburgh are not accessible to most readers. It is curious 

 that capitals are retained in this memoir in specific names, though 

 they have long since been abandoned in Survey memoirs dealing with 

 England and Wales. A number of plant-remains have been described 

 from the Caithness Flags, but the names of none of these appear in 

 the memoir, though we are informed that the plants collected were 

 submitted to Dr. Kidston for identification. 



One of the most striking features of the Orcadian rocks of Caithness 

 is their enormous thickness, which has been estimated at from 16,000 

 to 18,000 feet, which, however, includes 5,000 feet attributed to the 

 Thurso Flags. The present writer has given reasons for believing that 

 this is excessive, and the evidence furnished by the memoir points in 

 the same direction. The question is complicated by the extent to 

 which the rocks in the interior are obscured by Quaternary deposits, 

 the repetition and lateral variation of lithological characters, the 



