342 GEOLOGICAL APPEARANCES 



102. The preceding details afford grounds for the following 

 general statement of some of the most important facts. 



103. The mountain along the southern side of Glen Tilt 

 consists almost wholly of primary strata; that on the northern 

 is formed chiefly of sienitic greenstone^, with gradations into 

 sienite. Through the bottom of the valley the rocks consist 

 partly of stratified substances, and partly u crystallised aggre- 

 gates, which are commonly sienite, but in one or two places 

 sienitic greenstone. (Paragraphs, 11 to 34, 66.) 



104. The great body of strata on the southern side of the 

 valley, forming the base of Ben y Gloe, dips towards the south- 

 east ; and some stratified rocks on the southern bank of the ri- 

 ver, which, from their situation and general conformity, appear 

 to be connected with this great body, have main rocks of 

 the sienite lying under them. (Parag. 49, 50, 56.) The 

 sienite may therefore be considered as occupying a position 

 lower than that of these strata *. 



105. The lines of junction between these stratified rocks and 

 the sienite are in most places distinct. (Parag. 49, 50, 56, 

 58.) 



106. The strata, which occur, with scarcely any visible inter- 

 ruption, through the lower part of the Glen towards Blair, 



and 



* It must be observed, that the fact of the sienite lying under these primary, 

 or primitive, strata, is inconsistent with the geognosy of Werner, who assigns 

 to sienite a place in his Overlying Primitive Formation, that is, in a class of stra- 

 ta, which, according to him, always rest on the primitive strata, when those of 

 the two classes are found in contact. 



