Mr. Wm. Stevenson on Primary Quartz Bock, 8fc. 123 



character as those of the Greenlaw conglomerate, yet de- 

 serves special notice, from the evidence which it fur- 

 nishes of the existence of granular Quartz Kock in the 

 south of Scotland prior to its formation. This stratum, to 

 which the attention of the writer was first called hy the late 

 Miss Darling of Priestlaw (a lady who took much interest in 

 geological pursuits), is ahout four yards thick, nearly vertical, 

 and occurs between beds of arenaceous greywacke at Johns- 

 cleugh, near the source of the Whitadder. In position it is 

 strictly conformable to the strata with which it is associated. 

 It contains, besides fragments of clay-slate, felspar, and white 

 crystalline quartz, rounded masses of granular quartz of all 

 sizes up to five or six inches in their longer diameters, the 

 whole being firmly cemented by a very hard base of fine 

 grained greywacke. Although these pebbles differ in appear- 

 ance from those found in the Old Red Conglomerate of 

 Greenlaw, &c., it is not improbable that both may have been 

 derived from strata of the same formation which once existed 

 in the south of Scotland. Such appears at least much more 

 likely, than that they should have been transported from 

 Islay, Killiecrankie, or Braemar, the nearest localities where 

 a similar rock is now found in situ. 



If the above inferences are correct, we have a clue to a 

 more distinct knowledge of the geological structure of this 

 part of the country. The subject, though obscure and some- 

 what difficult, is assuredly not without interest, relating as 

 it does to an era of inconceivably remote antiquity in the 

 history of this portion of our planet. 



Since the foregoing paper was written, the writer, struck 

 by the resemblance of the quartz of which these pebbles consist 

 to the auriferous quartz of Australia, California, &c., sent 

 some samples to Dr. Stevenson Macadam for quantitative 

 analysis. Dr Macadam reports that the most refined tests 

 failed to shew the slightest trace of the presence of gold. The 

 quartz is very pure, consisting of — 



Silica, 99.37 



Oxide of Iron, 0.56 



Carbonate of Lime, .. . 0.07 



100.00 



