1800.] CKIKIR — OLD RED SANDSTOITE. 317 



belonged to the Old lied scries. Below these pale sandstones, no 

 rock is visible in the streamlet for some way, until at last we come 

 to Carboniferous sandstones, shales, and limestones, full of fossils, 

 dipping northerly at 5°— 10°. These occupy the bed of the Burn for 

 a short distance, when the dip changes to W., and they then sweep 

 round the west side of the Nethan Valley, as far down as the foot- 

 bridge, where they cross the river and ascend the valley on the east 

 side. Their boundary-line then turns sharply round to the north, 

 skirting the side of Black Hill, and curving round the north end of 

 that hill, down into the vale of the Clyde near Crossford. By com- 

 paring the line now described and its attendant dij)s with the strike 

 of the Old Bed Sandstones, it wih at once be seen that the one is as 

 nearly as may be at light angles to the other. The Bed Sandstones 

 dip steadily eastward at considerable angles, while the Carboniferous 

 undulate gently to the north and north-west. It cannot for a 

 moment be held that any fault intervenes between the two forma- 

 tions ; for the sinuosity of the junction-line and the undisturbed 

 position of the Carboniferous beds forbid such an explanation. 



There is only one locality in this part of the district where the 

 actual base of the Carboniferous series is seen. It is in the channel 

 of the Nethan, below the foot-bridge already referred to, where a set 

 of Carboniferous sandstones, with large stems of Lepidodi ndton and 

 Sigillaria, graduates downwards into a conglomerate, resting on a 

 porphyritic felstone in the Old Bed series. These dykes of felstone, 

 as 1 have already remarked, never cut through Carboniferous strata. 

 It is presumable, therefore, that they arc older than these. But in 

 the present instance, not only does the igneous rock not penetrate the 

 Carboniferous conglomerate, but the conglomerate is really to a con- 

 siderable extent formed out of the felstone, since its paste in the 

 lower part is highly f'elspathic, and contains moreover distinct frag- 

 ments of the peculiar rock on which it rests. The larger number of 

 fragments composing the conglomerate consist of the whitish sand- 

 stone which I have described as occurring at the Kerse Gill. Hence, 

 though we cannot sec here the Carboniferous series actually resting 

 on Old lied Sandstones, we yet find it formed partly out of the latter 

 ami partly out of igneous rock, which was intruded into the older 

 series before the deposition of the Carboniferous group. 



The evidence from the tianks nf Black Hill is very satisfactory. 

 That hill consists of an enormous protrusion of porphyritic felstone, 

 ha\ing a general bedded f>nn on the great scale, and dipping to the 

 easl along with the <Md Red Sandstones among which it has been 

 intruded. It is underlaid by hard purplish-grey' sandstones, which 

 can be seen at differenl points towards the south end. dipping 

 E. by N. :it from 20 to 30 . On the easl side of the hill similar 

 sandstones supervene; they are admirably shown in the channel of 

 the Clyde, where the dip is still easterly, al from 30 to !•"• . It is 

 on the truncated ends of these sandstones thai the sandstones, shales, 

 and limestones of the Carboniferous Beries have been deposited. 



Nothing can be clearer than the general relation of the rooks 

 along the west Sank of Black Bill. The coals there have Keen 



