THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE V. VOL. IX. 



No. I.— JANUARY, 1912. 



I. — Note on a Nepheline-Syenite Boulder deedged from the 



Atlantic. 



By Lady Eachel Workman McEobert. 

 rpHROXIGH the kindness of Dr. Flett there has come into my 



i hands an interesting boulder of nepheline-syenite belonging to 

 Sir John Murray, dredged during the expedition of the Michael Sars (1) 

 from the Atlantic Kise at a depth of 1,750 fathoms at a place about 

 150 miles south-west of the south-western corner of Ireland (Station 95 

 of the Reports of the Michael Sars Expedition). The slices examined 

 were slides Kos. F 2092 to F 2095 from the Geological Survey Collection 

 and two belonging to Dr. Peach. It is a boulder of remarkable 

 freshness, and so entirely unlike any other specimen as yet recorded 

 from the floor of the Atlantic that the question of its origin is of some 

 interest. The fact that no other fragments of the same type were 

 obtained in this dredging militates against the view that it is part of 

 a mass in situ on the sea-bottom. Its companions from the same 

 station, and in fact all the specimens collected by the Michael Sars, 

 have been recognized by Dr. Peach and Dr. Flett as similar to rocks 

 occurring commonly in Ireland, the North-West Highlands, and the 

 Southern Uplands of Scotland, and not one among them is closely 

 related to the nepheline-syenite. Rocks of Irish types have also been 

 described by Professor Cole and Mr. Crook (2) as a result of earlier 

 dredgings of the Atlantic floor, and again no specimen has been found 

 remotely resembling the subject of this paper. It would appear 

 likely, then, that this syenite boulder is of foreign origin and that it 

 has been transj)orted by floating ice moving southwards — an interpre- 

 tation suggested by Dr. Peach for most, if not all, of the associated 

 rock-fragments, which it is important to note were found embedded 

 end-on in the ooze and, probably owing to bottom currents, not 

 entirely covered up by silt. This he inferred from the distribution of 

 the adherent organisms still to be found on the stones. Perhaps this 

 syenite is derived from an unknown outcrop on the west of Ireland 

 or Scotland, or on the sea-bottom off' there. The shape of the boulder 

 unfortunately gives us no assistance in the question of its origin. 

 It is an angular block 6 by 2 by 4^ inches, shows no ice moulding, 

 and has evidently been lying in the ooze near the surface. It is 

 hoped that the description given below may some day lead to the 

 identification of its source, although at present this important point 



must be left in doubt. 



decade v. — VOL. IX. — NO. I. 1 



