824 



J. GELKIE ON THE GLACIAL PHENOMENA 



Its stones and boulders are of the usual shape, blunted and sub- 

 angular, and occasionally show well-marked strise. In size they 

 vary up to blocks 4 or 5 feet across, and consist chiefly of gneiss ; 

 but fragments of red sandstone &c. also occur. They are often very 

 irregularly disseminated through the matrix, in some places being 

 pretty equally distributed, in other places gathering more closely 

 together, so as to form now and then a pell-mell assemblage of 

 stones and boulders, with only a meagre matrix of clay. Broken 

 shells are sparsely disseminated throughout the matrix, appearing, 

 however, to be nowhere so plentiful as in the Lower shelly Boulder- 

 clay. They seem, indeed, to be quite absent from some of the ex- 

 posures ; for we searched the upper parts of the cliffs in several 

 places without being able to detect a trace of any thing organic. A 

 few fragments too small for determination were obtained at Port 

 of Ness ; but the only recognizable fragments came from the cliff- 

 section at Traigh Shuainaboist: they were Balanus balanoides, 

 Cyprina islandica, Saceicava norvegica, and Turritella terebra. 



The Upper shelly Boulder- clay is generally separated from the 

 underlying interglacial beds by a more or less well-defined line; 

 there is often, indeed, a strongly marked unconformity between 

 them, but occasionally the junction is much confused, and here and 

 there the beds seem almost to pass into each other. 



At Port of Ness a thick mass of coarse shingle, gravel, and sand 

 caps the cliff, and appears to pass down into sandy boulder-beds, 

 some stratified portions of which consist of shelly grit, gravel, and 

 sand. These deposits overlie, and form probably a modified portion 

 of the Upper Boulder-clay, into which they seem to pass. 



The annexed sections (figs. 2-5) will further illustrate the appear- 

 ances presented by the drift-deposits just described. The cliffs 

 shown in the illustrations vary in height from 30 feet up to 70 

 or 80 feet. 



Pig. 2. — Cliff-section south of Traigh Chrois. 



a. Lower Boulder-clay, with a few broken shells, sandy, unstratified ; stones 



subangular and blunted. 



b. Brick-clay and silt, dark-blue and grey; sandy; a few sporadic stones; 



broken shells. 



c. Stratified sand. 



d. Upper Boulder-clay, brownish, unstratified ; no shells seen here. 



Depth of section about 70 feet. 



In this and other figures the horizontal tint marking the Boulder-clay is not 

 intended to represent lamination or bedding. 



