1852.] NICOL ON THE GEOLOGY OF CANTYRE. 409 



at the foot of Ben Gollion, near Lime Craigs, and is also quarried on 

 the north side of the Mull district of mica-slate near Achinlisaig. 



The dip and direction of a contorted rock, like mica-slate, are neces- 

 sarily very variable and so far uncertain. In this district they can, how- 

 ever, be determined with considerable accuracy, as the rock is often well 

 exposed in sections. The dip ranges from about 12° or 15° up to 60° 

 or 70° ; but on the whole low angles predominate, and an average of 

 seventy observations gives about 30°. The direction of the dip is re- 

 markably uniform, and almost invariably to the east. Thus in seventy- 

 four observations sixty-three were to the eastward, and of these fifty- 

 seven to east by south. The mean direction of the dip is to S. 57° 26' 

 E. by compass, or allowing 25° for the variation to E. 8° S. (S. 82° E.). 

 In other words, the average direction of the strata is almost identical 

 with the general direction of the peninsula, which is thus merely the 

 outcrop of a system of beds of mica-slate. The same direction is found 

 very constantly as the result of direct observation in the district near 

 the Mull, where the strata have been little intruded on by recent ig- 

 neous rocks, and it thus appears not merely as the average, but as in 

 reality the original or normal dip of this series of beds. In confir- 

 mation of this view, it may be mentioned, that a fourth of the dips 

 observed in the region generally were within 3° of the average deduced, 

 and nearly one half not more than 10° from it. On the north-east 

 side of Ben Gollion, however, a more northerly direction prevails, the 

 strata dipping with few exceptions about 10° north of true east. 



The dip of the limestone series, noticed as connected with the mica- 

 slate on the north of Campbeltown, does not coincide with that just 

 deduced, or with that of the mica-slate in the same locahty. In 

 eighteen observations, sixteen were to the south-east, one south, and 

 one north-west, and omitting the latter, the mean of the whole gives 

 a dip of 34° to S. 32° E., or, with one doubtful observation omitted, 

 of 32° to S. 30° E. by compass, or S. 55° E. of true direction. This 

 group of rocks, therefore, has a slightly higher dip, and to a point 

 about 25° further south than the mica-slate. This might induce us 

 to believe that the limestone formed a distinct portion of the primary 

 series, but is perhaps owing to the great intrusion on the north of 

 trap-rocks which in this district are almost constantly associated with 

 the limestone*. 



The mica-slate forms the general base of the country, on and around 

 which all the other stratified formations have been deposited. The 

 first of these is red sandstone and conglomerate, occurring, as the 

 map (PI. XXIII.) will show, chiefly on the east and south-east of the 

 district. The relation of these rocks to the inferior formation is most 

 distinctly exhibited in the narrow valley of the Glenramskill Burn, 

 about one mile and a half east of Campbeltown. The west side of this 

 valley is composed of slate, forming the declivity of Ben Gollion, and 

 dipping on an average at 25° to 30° to E.S.E. (S. 75° E.) by compass. 



* The same association of igneous rocks with limestone beds is seen in the Si- 

 lurian rocks of Peeblesshire described by myself, and in those of Ayrshire de- 

 scribed by Sir R. Murchison, and is so constant that we can hardly regard it as 

 accidental. 



