Reports and Proceedings. SS.5 



lieights that extend across Scotland in a north-east and south-west 

 direction from Androssan on the Clyde to near Montrose on the 

 north-east coast ; they are continuous, although now only under the 

 Clyde, with the trap-hills of Renfrewshire. The age of these great 

 igneous outbursts — always a subject of interest to those engaged in 

 their investigation— can only be satisfactorily determined by the age 

 of any sedimentary strata, which they overlie, erupt, or otherwise 

 disturb. The officers of the Geological Survey, in their new sketch 

 map, have coloured this great chain of trap-hills as of Old Red 

 Sandstone age, holding that they were erupted before our Carboni- 

 ferous strata were deposited. If such were the case, they ought not 

 to be found overlying or altering the beds along their margins, as it 

 has been clearly shown they unquestionably do in many sections 

 along their course through our western coalfield, and as the section 

 which he now brought under their notice- not less clearly proves. 

 The section he referred to may be seen in Auchentorlie Glen, an 

 interesting ravine on the hillside, immediately to the west of the 

 village of Bowling. On entering the glen a little to the north of 

 the Dumbarton Road, the stream is seen to have cut its way through 

 an overlying bed of greenstone containing crystals of glassy felspar, 

 which rock forms the sides of the glen in its lower reaches, and dips 

 southwards towards the Clyde. A little way up on the left-hand 

 side, there is a cave-like recess under the trap, partly filled with 

 water, which has been formed by the scooping out of a bed of coal 

 and shale which crop out near the level of the stream. The trap is 

 here seen resting on the coal, which dips to the south-west at an 

 angle of 26 degrees, and is about two and a half feet in thickness. 

 It is considerably burnt in its upper part, but some of it gives off a 

 little flame. Between the coal and the trap there is a thin bed of 

 clay shale, and another shale underlies the coal ; but its tliickness 

 cannot be ascertained, owing to its position on the level of the 

 stream. The trap, where in contact with the coal, has been changed 

 into a lightish coloured rock, but a little higher in the bed it resumes 

 its normal tinge of a dark blueish grey. A few yards higher up the 

 glen, there is a small waterfall, wlrere the stream tumbles over a 

 ledge of the trap which overlies the coal. The strata here dip to 

 the south-east at an angle of 24 degrees. The coal-bed stretches 

 right across the stream, and is overlaid by, and rests on, clay shale 

 as in the former section ; but without boring it is impossible to say 

 what thickness of coal strata may exist here, nor, in the absence of 

 organic remains, can the relationship of this bed to our other Coal 

 strata be satisfactorily ascertained. That it belonged to the coal 

 Measures proper he had little doubt, although occurring nearly two 

 and a half miles within the trappean border ; but whether its position 

 was above or below the Hurlet or Campsie series he could not say. 

 However, the fact that the lowest bedded traps of this part of the 

 Kilpatrick range rest directly on Carboniferous strata, which they 

 have also burnt on the upper side, cannot be gainsaid, and they can- 

 not, therefore, be of Old Red Sandstone age, as assumed by the 

 Government surveyors. 



