204 THE OLD RED SANDSTONE. 
sionally pass a continuous wall, built at two different periods 
‘and composed cf two different kinds of materials: the one 
half of it is forraed of white sandstone, the other half of a 
dark-colored basalt; and the place where the sandstone ends 
and the basalt begins is marked by a vertical line, on the one 
side of which all is dark colored, while all is of a light color 
on the other. Equally marked and abrupt is the vertical line 
which separates the triple-barred from the conglomerate cliffs 
of the ravine of Eathie. The ravine itself may be described 
as a fault in the strata; but here is a fault, lying at right an- 
gles with it, cn a much larger scale: the great conglomerate 
on which the triple bars rest has been cast up at least two 
hundred feet, and placed side by side with them. And yet 
the surface above bears no trace of the catastrophe. Denud- 
ing agencies of even greater power than those which have 
hollowed out the cliffs of the neighboring coast, or whose 
operations have been prolonged through periods of even more 
extended duration, have ground down the projected line of 
the upheaved mass to the level of the undisturbed masses be- 
side it. Now, mark further, as we ascend the ravine, that 
the grand cause of the disturbance appears to illustrate, as it 
were, and that very happily, the manner in which the fault 
was originally produced. The precipice, over which the 
stream leaps at one bound into the mossy hcllow, is com- 
posed of granitic gneiss, and seems evidently to have intrud- 
ed itself, with much disturbance, among the surrounding 
conglomerate and sandstones. A few hundred yards higher 
up the dell, there is another much loftier precipice of gneiss, 
round which we find the traces of still greater disturbance ; 
and, higher still, yet a third abrupt precipice of the same 
rock. ‘The gneiss rose, trap-like, in steps, and carried up the 
sandstune before it in detached squares. Each step has its 
