1853.] HARKNESS KIRKCUDBRIGHT SILURIANS, 185 



Bay, is composed of strata analogous to those of the main land on 

 the eastern side of the Bay, as, indeed, the strike of the latter would 

 have led us to expect ; these have already been described by Mr. 

 Thomas Stevenson*. Here the black shales with Graptolites occur, 

 with greywacke, and trap-dikes. On the west side of the Bay similar 

 strata are found in the Big Ross, on the N.E. side, at Manor Point, 

 dipping S.S.E. at 60°. North of this, on the north side of Balman- 

 gan Bay, the dip is in the same direction, at an angle of 55°, and 

 here beds having a diiferent aspect appear ; and, on following the 

 west side of Kirkcudbright Bay northward, these rocks form the coast 

 to near the town of Kirkcudbright. They bear a great resemblance 

 to the general mass of rocks composing the lower Silurians of the 

 South of Scotland, and differ essentially in character from those de- 

 scribed in this paper. In some localities they are conglomeratic, and 

 they have a more regular S.E. inclination than any deposits lying on 

 the other side of the Bay. These lower silurians are not altogether 

 devoid of flexures, but these are local and of small extent. 



The prevailing inclination of the lower silurians of the South of 

 Scotland is towards the N.N.W. at a high angle ; but the S.E. and 

 S.S.E. inclination of these rocks in the Parish of Borgue is the result 

 of the intrusion of the Tongueland porphyry. This S.E. dip, pre- 

 vailing along this coast to the Headland of the Big Ross, is regarded 

 by Mr. Harkness as having existed previously to the deposition of 

 the upper silurians (as these are developed at Balmae) ; and he ob- 

 serves, that "the circumstance, that these lower silurians have not 

 been acted upon by the forces to which the Balmae beds owe their 

 contortions, tends to show a difference in the age and position of these 

 two series of strata. There is another circumstance, he adds, which 

 indicates that the prevailing inclination obtained prior to the deposi- 

 tion of the Balmae beds. This is the occurrence of a rounded frag- 

 ment of syenite amongst the shales in which the nodules containing 

 fossils are found ; and, as this syenite is identical in its nature with 

 those forming the axes of the lower silurians, it had in all probabi- 

 lity been derived from some of these, and thus it supports the in- 

 ference that the S.E. or S.S.E. dip which resulted from the intrusion 

 of this syenite must have prevailed anterior to the deposition of the 

 shales in which this fragment of the igneous rock is found. On the 

 whole, if we take the evidence of the fossils at Balmae, — the differ- 

 ence in the lithological character of the beds here, and of those which 

 lie to the northward, — the extent of flexure which characterizes the 

 former, and the occurrence in them of igneous dikes of a distinct 

 nature from the intrusions which have elevated the latter, — I think 

 there is sufficient proof of the later deposition and contortion of the 

 Balmae beds. Where we have a series of beds elevated at a high angle, 

 and sometimes nearly approaching the perpendicular, succeeded by 

 contorted beds, which have been much-denuded, and which also assume 

 a perpendicular position, it is difficult to determine the exact point 

 where the two formations come in contact ; but, judging from the 

 general occurrence of the more uniform S.S.E. dip on the north side 

 * Edinb. New Phil. Journ. vol. xxxv. p. 83. 



