68 B. N. Peach and J. Some — The Glacial ion 



crossed the low grounds of that country from the S.E. towards the 

 N.W. His faith in the north-westerly movement in Unst seems 

 then to have wavered, but no subsequent opportunity was afforded 

 him of re-visiting Shetland to examine the evidence anew. 



To quote further from the address : " Mr. Peach is a geologist of 

 such experience and strict accuracy that observations hy him need no 

 corroboration ; but Professor Geikie, in an article in ' Nature,' of 

 17th September, 1877, refers to the foregoing report by Mr. Peach, 

 and says that from his own observations he can speak confidently as 

 to the correctness of Mr. Peach's determinations." In the article 

 referred to, Professor Geikie confirms Mr. Peach's determinations 

 only with reference to the occurrence of abundant striated rock 

 surfaces, and Boulder-clays with striated stones, in the Shetland 

 islands, the existence of which had been doubted by S. Laing, Esq , 

 M.P. He carefully avoids exj)ressing any opinion regarding the 

 direction of glaciation of these islands, and so far as we are aware he 

 has never published any opinion on this question. 



Mr. Milne Home further says : " With regard to the vs^est coast of 

 the islands, where the markings are N.W. and S.E., the authors 

 state that these indicate a movement from the S.E, But the nature 

 of the evidence to show that the movement was from the S.E. and 

 not from the N.W. is not given." 



We are at a loss to understand how any one who has attentively 

 read our description of the Boulder-clay sections, could possibl}'' 

 conclude that the nature of the evidence for the north-west move- 

 ment on the west side of the Mainland is not given. We described 

 with considerable minuteness a series of Boulder-clay sections' ex- 

 tending across Northmavine from Ollaberry by Hillswick, Braewick. 

 Tan wick, to the Grind of the Navir and similar sections along the banks 

 of Eoeness Voe. On referring to the map accompanying our paper, it 

 will be seen that the lithological A-arieties of the rock-masses along 

 these lines of section are so distinct as to render it an easy matter 

 to determine the direction of the ice-movement, from the dispersal of 

 the stones in the Boulder-clay. We distinctly indicated that the ice- 

 carry between the diorite area east of Hillswick and the cliff's north 

 of the Grind of the Navir was toivards the north-west. We pointed 

 out that the quartz-felsite and granitic area Avas invaded by the 

 diorite stones, and the area occupied by the contemporaneous por- 

 phyrites and tuffs was invaded by the diorite and quartz-felsite 

 stones ; the relative ingredients diminishing in num.ber in proportion 

 to the distance from their parent source. Furthermore, in the 

 peninsular tract which lies to the west of Weesdale, we stated that 

 corroboratiA'e evidence is obtained of this noi'th-westerly movement 

 on the west side of the Mainland. To the east of the north and south 

 bounding fault which crosses the peninsula from Aiths Voe to 

 Bixetter and Selie Voes, no trace of the altered Old Eed Sandstone 

 rocks are to be found, either in the Boulder-cla}'^ or on the surface, 

 while numerous blocks of the epidotic syenite and the associated 



1 Quart. Journ. Geol. Soc. vol. xxxv. p. 796, et seq. 



