388 Proceedings of the Royal Physical Society. 



of the Koyal Society of Edinburgh," vol. iv. p. 200. This 

 digression from my glacial story, I trust, is of sufficient 

 interest to be pardoned. 



In addition to the glacial markings on the rocks, I met 

 with several deposits of drift, in which rounded, striated, 

 and smoothed stones were not uncommon, some of the 

 deposits being from 12 to 14 feet in depth. Perched blocks, 

 but not in abundance — some of large size — are scattered 

 about, and, with the rounding and smoothing of the face of 

 the rocks, are to be found over all this group of islands. 



Unst. — Our next move was to Unst, the harbour of Balta 

 Sound being our head-quarters. Here, too, the effects of 

 glacial action were plainly to be seen. The serpentine rock 

 has suffered seriously ; and although much acted on by 

 rain, frosts, &c, the rounded outline of the hills tells plainly 

 of the grinding they have undergone. Euts and striae are 

 also rare here. I met with a few on the cliff at Hagdale, 

 in Haroldswick Bay, where there is a thick deposit, com- 

 posed of clay, in which polished and striated stones, of 

 various sizes, are plentiful. Part of this deposit had recently 

 slipped off the rock, and here the markings were as 

 splendidly shown as if the grating masses had only passed 

 over it a few days before. The direction of the striae, &c, 

 are nearly W.N.W. and E.S.E. The hills of the Muckle and 

 Little Heogs lie to the north of this spot (Hagdale), and a 

 slope from about 20 feet above the level of the sea hence 

 to the top of the Muckle Heog, rises gradually to the height 

 of at least 500 feet. In this slope lies the famed mine for 

 chromate of iron. On reaching the top of this hill I found 

 the W.N.W. end vertical and polished, to the depth of at 

 least 150 feet, and before it a depression is formed, remind- 

 ing me much of that in front of Arthur's Seat and Salisbury 

 Crags. The hills to the north of the Heogs slope towards 

 it, and down these, no doubt, the crushing agents came. The 

 vertical or storm side of the Heog 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 evidenced by the greater 



