54 ME. A. HAEKEE ON THE GEOLOGICAL [Feb. 1906, 



agglomerate. Since it cuts the dolerite-sills, it cannot be older 

 than the agglomerate, and its apparent truncation must be due to 

 the difficulty which it experienced in piercing that mass. Both in 

 its fofhi and in its relations this fragmental accumulation of Bidein 

 Boidheach closely resembles some of the small volcanic vents of 

 Skye, notably one in the cliff at Sgurr-an-Duine, between Lochs 

 Brittle and Eynort. 



The nature of the material is also in accord with this inter- 

 pretation. The principal element is amygdaloidal basalt, in blocks 

 measuring up to a foot or two in diameter, subangular or rounded ; 

 the rounding being of the kind characteristic of our volcanic agglo- 

 merates, that is tending to the spherical form, without the ovoid 

 shapes so common in waterworn pebbles. Torridonian rocks, in 

 smaller pieces, are fairly plentiful, and Sir Archibald Geikie found 

 fragments of the white sandstone of the Oolites. Both formations are 

 doubtless in place below sea-level at this locality, and the occurrence 

 of their fragments in a volcanic agglomerate is very natural. 

 Dr. Peach detected also a piece of granite and other fragments of 

 a decayed rock, probably of the gabbro-family. These plutonic 

 rocks occur also in the volcanic agglomerates of Skye, 1 and possess 

 a certain interest, which lies, however, outside our present subject. 

 The most significant fact is the absence of any fragments of dolerite 

 from the sills. In a river-gravel derived from the erosion of the 

 basalts and dolerites the latter should be as abundant as the former, 

 or more so in virtue of their superior durability. The character of 

 the material, therefore, confirms the conclusion that we have to do 

 here with a volcanic agglomerate of the basalt-period, much older 

 than the dolerite-sills and very much older than the pitchstone. 

 The conjunction of the pitchstone with the agglomerate is, on this 

 riew, merely accidental. 



The second locality to be examined is near the other end of the 

 ridge, on the southern side of the higher part of the Sgurr and 

 about a quarter of a mile from its easterly termination. It is 

 somewhat above the former occurrence, both in altitude and as 

 regards geological horizon. In this neighbourhood the brecciated 

 and decayed base of the pitchstone has been cut back to make a 

 recess or piazza, in places 10 feet or more in height. In the floor 

 of this recess a breccia with fragments of various rocks is poorly 

 exposed for some distance ; and at one place, near some shelters for 

 sheep, is the locality of the well-known fossil wood. 



Although the fossil wood of the Sgurr of Eigg was discovered 

 90 years ago, and has been referred to by numerous writers, the 

 published information concerning its mode of occurrence is not 

 only very scanty, but remarkably confused. This is due partly to 

 misunderstanding of records obtained at second-hand, partly to the 

 fact that wood occurs at this place in more than one situation and 

 of more than one kind. 



1 ' The Tertiary Igneous Kocks of Skye ' Mem. Geol. Surv. 1904, p. 24. 



