E. B. Bailey— The Sgurr of Eigg. 301 



it extends for some fifty yards it does not seem possible to the writer 

 to form a definite opinion regarding its relations. What is more 

 immediately attainable is the determination of the precise nature of 

 the pitchstone-breccia. A very thin and irregular representative of 

 this breccia occurs along the steeply inclined base of the pitchstone- 

 felsite complex where the latter terminates in the Sgurr. A specimen 

 •was taken at a point somewhat above the topmost sheet lettered D in 

 Fig. 2. It had the appearance in the hand of being a completely 

 fragmental rock, and as it was fresh — unlike the breccia farther 

 west, which has been weathered to give the recess YZ (Fig. 2) — it 

 was sliced and examined microscopically. The fragmental nature is 

 clearly shown in the slice (PI. XXII, Fig. 2). The fragments are pitch- 

 stone in widely different stages of crystallization, detached and broken 

 porphyritic felspars derived from the pitchstone, and basalt — one small 

 piece of basalt, unlike the others in character, is enclosed in a pellet 

 of glassy pitchstone.' A cement of calcite fills the interstices of the 

 breccia. 



Some of the weathered breccia of the recess farther west seems to 

 have a definite pitchstone matrix, but some again seems to the eye to 

 be completely fragmental like the specimen just described. At any 

 rate, the occurrence of a genuine fragmental breccia (as opposed to 

 a mere xenolitbic rock) at the base of the pitchstone has now been 

 demonstrated, however local the occurrence may be. My own 

 experience leads me to take this as a proof tliat the pitchstone is 

 a lava. It is a common thing to find definite breccia at the base of 

 lava-flows. In some cases the breccia has resulted from a preliminary 

 shower of ash ; in others it is the debris which has slid down the 

 advancing front of the lava. But is it possible to point to any 

 example of an undoubted sill with an open breccia constituting 

 its base ? 



2. At its north-western end the pitchstone ridge terminates abruptly 

 in a sea-cliff, and there is exposed beneath the pitchstone about 

 a hundred feet of fragmental material (Fig. 3). 



With a rope and a trusty companion one could examine at ease the 

 glorious natural section afforded. Like my predecessors, however, 

 I came all unarmed, and had to content myself with hammering over 

 a small part of the fragmental deposit at the south side on the cliff- 

 top. The actual hammering is of course supplemented by the very 

 fine view obtained — especially from the base of the cliff, which can 

 be reached at low-tide after first descending to the shore by a stream- 

 valley some little way farther north. 



' Anyone wishing to see this xenolithic fragment, which is not shown in the 

 photograph, will find it in a corner of the Survey slice 17181. Dr. Harker, 

 who has kindly examined two additional slice.-;, cut on his suggestion, has 

 drawn my attention to a similar xenolithic fragment on the margin of 17181c. 

 In the two cases the enclosed basalt is of one and the same type, and is 

 markedly distinct from the other pieces of basalt scattered throughout the 

 slices. Dr. Harker (p. 306) states his opinion that in a few cases glass is 

 adherent to these latter also. It is sometimes difficult in a slide of a breccia 

 to distinguish with certainty between mere contact and actual continuity, and 

 I am unable to agree with Dr. Harker in this particular, but fortunately the 

 difference in interpretation does not appear essential to the argument. 



