368 B. N. Peach ^ J. Home — Glaciation of the S/ief lands. 



impossible that ice coming from the north or west could transport 

 blocks of porphyritic granite in the Boulder-clay, from the north- 

 eastern headlands of Unst to the west slope of Saxavord Hill, or 

 striated stones of serpentine and gabbro to the west of the areas 

 occupied by these rocks. When the foregoing facts were laid before 

 Mr. C W. Peach, in the summer of 1878, he readily perceived the 

 conclusive nature of the evidence regarding the westerly flow of the 

 ice in Unst, and he frankly admitted that he had been misled by 

 the glaciated appearance of " the W.N. W. end " of the Heog Hill. 

 In the words of his recent letter, though he noticed the bearings of 

 the strife right, he was wrong as to the direction of the drift. 



3. Mr. Milne Home further says: "Unst, however, is not the 

 only island where a discordance exists between Mr. Peach's observa- 

 tions of the strise and those of Messrs. Peach and Home. Mr. 

 Peach, senior, examined Whalsay, a small island situated a few 

 miles to the east of the Mainland, and therefore one of the first 

 spots which would be passed over by the alleged Scandinavian Ice- 

 sheet. Messrs. Peach and Home say of this island that, on both 

 sides of it, there are striations, showing an average movement 

 towards S. 28° W. On the other hand, Mr. Peach, senior, says that, 

 not satisfied with taking the direction of the striae at places where 

 he found the rocks exposed, he removed the drifted clay and stones, 

 in order to obtain a fresh surface ; and the scratches at all the places 

 (he says) ' run nearly east and west,' — which, by true bearings, 

 would be E.S.E. and W.N.W. Here, again, is discordance between 

 Mr. Peach, senior, and the authors of the paper." 



This passage is an example of the curious misapprehension of the 

 facts, of which we complain. The alleged discordance is utterly 

 groundless. Mr. Milne Home here confounds Whalsay with the 

 Outskerries of Whalsay, which lie about five miles to the E.N.E. of 

 that island. In point of fact, Mr. Peach, senior, never examined the 

 glacial phenomena of Whalsay at all, but he visited the Outskerries. 

 Besides, Mr. Milne Home makes another serious error, amounting 

 to about 46°, in making allowance for the magnetic variation. Mr. 

 Peach states in his paper that he found stri^ only at two localities 

 in the Outskerries, which "ran E. and W."' (magnetic). By 

 referring to the table on a preceding page, it will be seen that in 

 1864 E. and W. magnetic = E. 24|° N. and W. 241° S. 



In the course of our visit to the Outskerries, we noted 19 instances 

 of striations, which we summarized in our paper as follows : " In 

 Gruna the striae vary from S. 10° W. to W. 42° S. ; in Brury, on the 

 top of the highest hill, S. 35° W., and in Housay S.S.W. to S.W." 

 Instead of quoting the various examples, it will be suflScient for our 

 present purpose if we refer to some on Gruna, opposite the light- 

 house. In the Bay, east of the lighthouse keepers' dwelling-houses, 

 we observed several examples of ice-markings pointing W. 25° S. 

 The difference, therefore, between the true bearings of the striations 

 recorded by Mr. Peach and those we noted on the east side of 

 Gruna amounts to ^°. Any one accustomed to map glacial stri^ 

 » Geol. Mag. 1865, p. 342. 



