372 B. JSf. Peach S^ J. Some — Glaciation of the Shetlands. 



Ness is composed of granite, which, according to Hibbert, was 

 " removed from a rock, the nearest site of which is about two miles 

 to the north." But this boulder might quite well have been derived 

 from some of the bosses of the same material lying at a slightlj'' 

 greater distance to the east and north-east of Hillswick. 



Mr. Milne Home also cites the "return" sent in by Mr. Russell to 

 the Edinburgh Royal Society Boulder Committee regarding seven 

 boulders of granite and gneiss in Foula. Mr. Russell suggests that 

 these have been transported from Culswick and Delting lying to the 

 north-east. He adds that from the middle of the island, at a height 

 of 700 feet, granite and gneiss drift occurs as far as the south end 

 of the island. Quoting from the statistical account of Scotland, Mr. 

 Milne Home says the island is composed of Old Red Sandstone. 

 He is evidently not awai"e of the fact that the eastern part of the 

 island consists of gneissose rocks with a mass of granite in the 

 north-east corner. We believe that Dr. Gibson was the first to point 

 out that the Old Red Sandstone of Foula was thrown against the 

 crystalline rocks by a north and south fault' — an observation which 

 we confirmed. The granite mass resembles the rock in Sandsting, 

 so that the boulders may have been of local origin, and we noted 

 several blocks of gneiss of local origin. We also observed that the 

 metamorphic rocks were borne towards the W.N.W. and N.W. on to 

 the Red Sandstone area, and in the Boulder-clay west of the fault 

 we detected a block of epidotic syenite from Dunrossness. The 

 later glaciers shed from the hills carried some Old Red debris on to 

 the area occupied by the gneiss. A fine series of moraines with the 

 usual concentric arrangement occurs in the valley draining the 

 north end of the island.^ 



Mr. Milne Home asks, how the occurrence of boulders perched on 

 ridges and hill tops can be explained on the supposition of a great 

 mer de glace, which overrode the whole islands and smothered them 

 in ice. To this we reply that some of the boulders were borne 

 forwards in the ground moraine, while others became fixed in the 

 lower portions of the ice-sheet, and were likewise carried along by 

 the advancing mass. As the ice melted backwards, the blocks and 

 angular debris were stranded at the localities where we now find 

 them, except where they were displaced by later movements. 



^ Brit. Assoc. Reports for 1876, p. 90. Dr. Gibson states that no fossils had been 

 found in the Old Eed Sandstone rocks of Foula. We were fortunate enough to 

 discover numerous specimens of Psilophyton princeps, Dawson, in shales in the north 

 of the island. Similar plant-remains occur in the sandstone near Lerwick and Sand- 

 lodge, on the east side of Shetland. 



* Had we been disposed to refer to the observations of others, which were not 

 corroborated by ourselves, we might have adduced the testimony of Mr. Milne Home, 

 regarding Norwegian boulders in Shetland. In an article entitled " Are there no 

 boulders in Orkney and Shetland P," Nature, vol. xvi. p. 476, he refers to certain 

 boulders reported to the Edin. Roy. Soc. Boulder Committee. Under the heading 

 "Bressay" the following statement is made: "A number of boulders here, of a 

 rock foreign to the island. One of them is 10 x 7 x 4 feet. Supposed to have been 

 transported from Norway." 



