108 Swanston— Silurian Rocks of Co. Down. 



do more than notice the rocks which occupy the north-eastern portion of the 

 area situated wholly in the County Down. 



PREVIOUS NOTICES OF THE DISTRICT. 



Perhaps the earliest reference to the rocks of this area is that by Drs. 

 Berger and Conybeare, made in 1816. (1) These pioneers of Irish Geology 

 pointed out the similarity between the County Down rocks and those of South 

 Scotland. On the large geological map compiled by Sir Richard Griffith in 1839 

 the area is put down as Clay-slate or Greywacke-slate belonging to the Transition 

 series. Dr. Bryce in 1852 stated as follows (2) : — "The County Down con- 

 tained two granitic tracts which seem to have been elevated at different epochs. 

 They are separated from one another, and each is wholly enclosed by a thick 

 band of metamorphic slate, gneissose in its lower part, and passing upwards 

 into flinty and common clay-slate. Superimposed conformably upon these are 

 other slates of less crystalline type, whose aggregate thickness is enormous, 

 and whose upper portions have yielded a few imperfect fossils, which seem to 

 make them referable to the Lower Silurian Group ; but as yet no definite line 

 has been made out to justify a classification." Sir Roderic Murchison states 

 in 1854 (3) : — "It is believed that the Schists of Down are of the same age as 

 the Graptolitic Schists of Wigton and Galloway." J. Beete Jukes, F.R.S., after 

 referring to the Chair of Kildare, which contains Bala fossils (4), states that 

 "another great tract of apparently similar beds stretches from the centre of Ire- 

 land, Cavan, &c, to the coast of Down. Among these, however, a portion 

 certainly belongs to the Llandeilo Flags, as near Bellewstown, on the confines 

 of Dublin and Meath, an assemblage of Llandeilo fossils were found." 



Many years ago it was known to members of the Club that Graptolites 

 occurred in the County Down, and specimens were obtained by them at Tully- 

 garvan, near Saintfield, from the debris of a shaft which was there sunk in the 

 Silurian rocks in search for coals (5); none were, however, sufficiently perfect for 

 identification. 



(1). Transactions of the Geological Society of London, Vol. III. 



(2). Report of the British Association (1852). 



(3). Siluria (1854) — foot note, p. 166. 



(4). Manual of Geology (1862), p. 454. 



(5). The slightest knowledge of the evidence furnished by these fossils would have saved a 

 vast amount of useless expenditure and misdirected efforts here, and at many other localities 

 throughout the district. The projectors in their search for coals were doubtless misled by the 

 resemblance of the black Graptolitic bands to the rich carbonaceous shales of the Coal 

 Measures. 



