148 GEOLOGY OF THE LOTHIANS. 



that they vary from a perfect distinct boundary line to one 

 of the most indefinite character, one in which the minerals 

 of the rock containing the concretions occur interlaminated 

 with those of the concretion. 



We shall now detail the relations of the granite to the 

 greywacke, which are observable at two points. The 

 Needle's Eye, a perforated rock which occurs near the 

 mouth of the South wick water, is a point where both rocks 

 may be found in immediate connection, and the first ap- 

 pearance, which is most striking, is the intimate blending of 

 the one with the other. The whole scene in this respect is 

 one of the greatest confusion, and certainly if the igneous 

 origin of granite were not supported by appearances more 

 indicative of a plutonic formation than those observable 

 here, its synchronism with the greywacke, and perfect simi- 

 larity of formation, would be based on no insecure founda- 

 tion. 



To describe all the minute modes of junction of the grey- 

 wacke and the granite at this point would, if the nature of 

 the ground did not render it impossible, be an unnecessary 

 labour; we shall, however, give a detailed account of their 

 junction taken as a whole. When considered as a mass the 

 granite of this point appears to be chiefly distributed through 

 the greywacke in the form of veins, which occur of all mag- 

 nitudes, and run courses which in some instances are al- 

 most straight, while in others they are highly tortuous. On 

 examining the immediate planes of junction of the granite 

 with the greywacke, these will be found to vary much 

 in appearance, sometimes both rocks having a decided 

 and well marked boundary, while at other times they make 

 a gradual transition into each other. Throughout the same 

 vein both of these appearances may sometimes be observed ; 

 one part, in some instances, affording a distinct separation,. 



