182 Professor Sepeawick on the 
can in any way be considered as a connecting link between the 
ordinary beds of the carboniferous series, and a mass of crystalline 
rock composed of pyroxene feldspathic earth and magnetic oxide of 
iron. 
The strata of the metalliferous formation are essentially com- 
posed of limestone, of sandstone, and of slate-clay. The strata 
immediately above and below the Whin-Sill, exhibit the same 
alternations, differing from other beds only in bemg more gra- 
nular or more indurated; and the change of texture is greatest 
in those which are in immediate contact with the Whin. In such 
localities, the beds of crystalline limestone are identified as true 
members of the great formation by their organic remains, which 
often exist in the same order and abundance in which they are 
found in other unaltered beds, only disappearing very near the 
trap where the limestone becomes completely and coarsely gra- 
nular. The beds of sandstone never lose their original texture, 
although, in some instances, they have undergone considerable 
modification. Some of the hard flinty beds are identified with 
the shale, by their slaty structure, and by other external charac- 
ters; occasionally also by imbedded nodules of iron-stone, 
and by organic remains. Close to the trap, the beds of shale 
are sometimes so much modified, that they entirely lose their 
identity, and it would be impossible to pronounce upon them 
by the help of any series of hand specimens. To understand their 
relations, it is absolutely necessary to examine them on the spot. 
In addition to what has already been stated, I think it im- 
portant to observe, that the changes above described, are the most 
remarkable, where the masses of trap, in contact with the other 
beds, are the greatest. Above Middleton, I did not examine 
a single locality where the strata, immediately above or below 
the Whin-Sill, had not undergone a very striking modification : 
but the dykes in Eglestone Burn, and the thin bed in the banks 
