B. N. Peach 8^ J, Home — Glaciation of the Shetlands. 367 



W. 10° S. A few yards south of previous instance. 



"W. 30° S. On shore near Lund, north of Belmont. South coast. 



W. 30° S. At Houlon Ness. West coast. 



W.jSr.W. Near Collaster. ,, ,, 



From this list it is apparent that the ice-markings must have been 

 produced by ice moving in a determinate direction along a W. and 

 W.S.W. line. There is only one exception, at Collaster, which 

 harmonizes with the north-westerly trend on the west side of Yell 

 and the Mainland. Indeed, when we consider that the stride occur- 

 ring at a height of 500 feet agree with those found on hill slopes 

 and at the sea-level, it is impossible to escape the conclusion that 

 the agent which produced them must have pressed uniformly on 

 hill and valley, along the lines indicated by the stri^. 



But the supposed ice-movement fi-om the hills round Saxavord 

 against " the W.N.W. end " of the Heog Hill is also disproved by 

 the dispersal of the stones in the Boulder-clay. On the west side 

 of the Saxavord Hill, overlooking Burra Fiord, a deposit of Boulder- 

 clay occurs at a height of 300 feet above the sea. The deposit is 

 about fifty feet thick. A considerable proportion of the included 

 stones consists of the characteristic hornblendic granite of Lamba- 

 ness and Scaw, about two miles to the east of Saxavord Hill. This 

 rock is easily recognized on account of its porphyritic character ; the 

 pink felspar crystals measuring upwards of two inches in length. 

 In our paper we pointed out that " ere these granite fragments could 

 have reached this position along the path line indicated by the striee, 

 they must have been transported in the moraine profonde across the 

 shoulder of Saxavord Hill, where it attains a height of 600 feet ; 

 whereas none of the Lambaness granite occurs in situ at a greater 

 height than 150 feet." 



Moreover, it was clearly pointed out in our paper that a careful 

 examination of the stones in the Boulder-clay on the west coast 

 proves beyond all possibility of doubt that the ice must have crossed 

 Unst from the North Sea to the Atlantic. Between Woodwick and 

 Wick Bay striated blocks of gabbro and serpentine occur in this 

 deposit, which have been carried across the intervening water-shed 

 nearly 700 feet high. We showed that the relative distribution of 

 the gabbro and serpentine stones in this deposit on the west coast 

 is in direct proportion to the respective areas occupied by these 

 rocks on the east side of the water-shed. The occurrence of these 

 blocks in the sections referred to cannot be disputed. Indeed, our 

 observations have been confirmed by Prof. Helland, of Christiania, 

 who arrived at similar conclusions regarding the westerly movement 

 of the ice in Unst.^ Mr. Peach's traverses did not extend to the 

 west coast, but he noted the occurrence of striated serpentine stones 

 in the Boulder-clay at Loch Watlea, to the west of the serpentine 

 area.* There is little wonder that this fact puzzled him very much 

 at the time, considering the hypothesis he adopted after a rapid 

 examination of only a portion of the island. It is physically 



^ Zeitschrift der Deutschen geologischen Gosellschaft, Jahrg-ang 1879, p. 716. 

 2 Geol. Mag. Feb. 1881, p. 67. 



