B. N. Peach 8^ J. Sorne—Olaciation of the Shetlanch. 365 



those islands pointed 24^° to the west of true north.^ It follows 

 therefore, that, 



Magnetic IST. = N. 24i° "W". true. 



Magnetic N.N.W. =N. 47° W. true, or nearly N.W. true. 



Magnetic N.W.=]St. 69|° W. true, or W. 20^° N. true. 



Magnetic W.N.W. = W. 2° S. true. 



Magnetic W.=W. 244° S. true. 



Mr. C. W. Peach recorded striations only from one locality in 

 Unst, viz. on the south side of Haroldswick Bay on the east coast 

 running W.N.W., and E.S.E, (magnetic).^ From the foregoing 

 table it will be seen that in 1864 W.N.W. magnetic = W. 2° S. 

 true, or nearly E. and W., as noted by us. There is thei-efore no 

 discordance between us so far as the mere trend of the ice-markings at 

 that locality is concerned. The ice which produced these markings 

 must have come from the east or west. Mr. Peach inferred that the 

 movement had been from the west, and this leads us to discuss the 

 evidence he adduced in support of this contention. 



2. In addition to the stri^ in Haroldswick Bay, the only 

 evidence advanced in his papers, in 1865, was the glaciated appear- 

 ance presented by "the W.N.W. end" of the Heog Hill, which is 

 thus described. On reaching the top of the Heog Hill (about 500 

 feet), he found "the W.N.W. end, vertical and polisbed to the 

 depth of at least 150 feet. The hills to the north of Heog Hill slope 

 down towards it ; and down these, no doubt, the crushing agents 

 came. The vertical and storm side of Heog Hill had evidently 

 resisted a portion of the destroyer, and turned the greater part on 

 its western flank, and thus the main body passed down the valley 

 towards Haroldswick, as evinced by the greater destruction there 

 than on the eastern side." 



A careful examination of that tract conclusively shows that Mr. 

 Peach was misled by the glaciated appearance of " the W.N.W. end" 

 of the Heog Hill ; indeed there can be little doubt that if he had 

 found time to examine the ground minutely, he would have had no 

 occasion now to regret " the oversight and neglect of the warnings 

 of Hammer and Watlea " referred to in his letter. A slight know- 

 ledge of the geological structure of the ground enables us to explain 

 the origin of the steep rock slope described by Mr. Peach. From 

 the south shore of Haroldswick Bay westwards to the Loch of Clitf 

 and Baliasta there is a ridge of hilly ground composed of serpentine 

 about two miles in length. The Crusafield Hill forms the western 

 termination of the ridge near the Loch of Cliff, while the Muckle 

 and Little Heog Hills are situated near Haroldswick Bay. On the 

 west, north-west, and north sides there is a steep declivity, but to 

 the east and south-east, the gradient is gentle. The boundary-line 

 between the serpentine and soft schists lying to the north and 

 west runs from Norwick Bay on the east coast to Baliasta, skirting 

 the north-west and west slopes of this hilly ground. This boundary- 



1 The true direction was 24° 35', which is, roughly speaking, 244°. This applies to 

 the middle of the group. Northwards from this there was a slight increase and 

 southwards a decrease in a regular ratio. 



2 See Geol. Mag. 18G5, p. 343. 



