Yol. 51.] ME. H. W. MONCKTOJf ON THE STIRLING DOLERITE. 



485 



x70. 



This junction at the top of the igneous rock resembles generally 

 the bottom-junction at Sauchie Craig and at Touchadam above 

 described. The top is 



marked by a well-de- -pig. 1.— Junction of basalt and shale. 

 fin eel , th ough i r regular 

 line, and at one spot 

 a projecting point of 

 shale is partially sur- 

 rounded by the ig- 

 neous rock. A por- 

 tion of a micro-section 

 cut through the top of 

 the rock is shown in 

 fig. 1. There is not 

 the flow-structure of 

 the Touchadam speci- 

 men, and the porphy- 

 ritic felspars are lying 

 at all angles. The 

 groundmass is, how- 

 ever, very dense, and 

 I think that if it were 

 slightly transparent 

 the lines of flow might 

 probably be seen 

 twisting in and out 



amongst the felspars, as at Touchadam. Indeed, in the portion 

 figured there are indistinct signs of flow-structure in the lower 

 part of the figure. 



The felspar is very well preserved, and in this the rock differs 

 from the bottom rock of Sauchie Craig and Touchadam. There is 

 here a more or less distinct spherulitic structure in the uppermost 

 zone, which is some 0-18 inch wide. 



The groundmass is mainly composed of oxide of iron for a 

 distance of about 1 inch from the top, and then minute crystals 

 of plagioclase appear in it, the larger porphyritic plagioclase-crystals- 

 continuing throughout. This rock effervesces with acid, but less sc- 

 at the top than 2 inches down. For other features of this locality 

 I would refer to Mr. Goodchild's account. 1 



Near Sauchieburn there is a good deal of the white altered shale 

 locally known as ' calm,' and it has been worked in a small pit at 

 the point marked 3 on the accompanying sketch-map. 



South-west of the house at Sauchieburn (see sketch-map, fig. 2 T 

 p. 486) the igneous rock rises in a picturesque cliff nearly 300 feet 

 high. If one climbs up it in a south-westerly direction one finds a 

 series of four ridges rising one above the other, composed of igneous 

 rock. In several places on the two lower ridges one may find 

 ice-marked surfaces of rock, and if these are carefully examined 

 it will be found that the scratched rock is the indurated shale, 

 1 Op. supra cit. 



