280 Reviews — Model of the Assynt Mountains. 



infrequency of fossils, and the possibility of the occurrence of 

 undetected faults. 



The igneous rocks intrusive in the Old Red Sandstone include 

 monchiquite and nepheline basalt, allied to the dykes of the Orkneys. 



Second only to the Orcadian rocks in interest are the glacial 

 phenomena, which are dealt with in considerable detail, and a full 

 account is given of the transported mass of Lower Cretaceous age 

 found at Leavad. The absence in Caithness of the 100 foot and 

 50 foot raised beaches that are so characteristic of the Scottish coasts 

 is attributed to a covering of ice, but it is possible that the former 

 may be represented by the beach found at a height of from 5 to 8 feet 

 above the sea, for there is evidence of recent depression. 



The colour- printed sheets 110 and 116 mark a great advance on the 

 hand-coloured sheet 115. It is a pity it was necessary to employ the 

 dark tints which have been allocated to Devonian rocks and render 

 the topography difficult to read, and the difficulty is increased by the 

 shading indicating the Quaternary deposits. A. small area south of 

 the Stacks of Duncansby is wrongly coloured as Caithness Flags 

 instead of John o' Groat's Sandstone. This has been set right in type, 

 but was correctly mapped nearly a quarter of a century ago. It is 

 interesting to note that after employing in turn white, black, and 

 blue for faults the Survey has now adopted dark reddish brown for 

 the same purpose. The only drawback is that it rather suggests 

 igneous dykes. 



J. W. E. 



III. — Geological Model of the Assynt Mountains. 



TI1HE North-West Highlands of Scotland from the time of Macculloch 

 J_ onwards have excited the attention of British geologists ; now, 

 thanks to their labours, and not least to those of Drs. Peach and Home, 

 the region stands as a type for the study of certain forms of earth - 

 movement and mountain-building. The geology of this region has 

 been fully described in the Survey memoir on The Geological Structure 

 of the North-West Highlands : it is, however, a bulky volume, and the 

 district itself is difficult of access ; therefore, to help those who are 

 unable to visit the ground to form a conception of the character and 

 results of the great earth-movements, a model has been prepared of 

 a selected portion. The model embraces an area of about 168 square 

 miles, and is on a scale of 6 inches to 1 mile (vertical and horizontal) ; 

 examples of it are exhibited in the Museum of Practical Geology, 

 London, and in the Royal Scottish Museum, Edinburgh. 



We have now before us a Guide to the Geological Model of the 

 Assynt Mountains, by Drs. B. N. Peach & J. Home, price Id., which 

 will be of the utmost assistance to students in arriving at an under- 

 standing of the model and of the great thrust-movements it exemplifies. 

 Some of the place-names will be a little difficult for the southerner ; 

 after a struggle with Beinn nan Cnaimhseag or Cnoc na Glas Choille 

 he may long for the military expedient of plain "Hill 60". The 

 pamphlet is illustrated by a sketch-map and a number of sections 

 which greatly assist in the interpretation of the geology. Within 



