186 Burton: The Cleveland Ironstone. 
shown 3 miles distant. In that short distance there has been 
a great alteration in the strata. The main seam has thinned 
down from 11 feet to 53 feet. The Pecten seam closely resem- 
bles that at Hummersea, which is nearly 11 miles distant 
from Eston. Any differences may be due to the difference in 
the mental attitude of different observers, in allotting this to 
Ironstone, that to shale, or to the difficulties attending accurate 
measurement. Still proceeding southwards to Ingleby (a 
distance of 5% miles from Roseberry), the Pecten seam (if 
correctly located and described, and I am taking the figures 
from the Survey records) bears no kind of relationship to 
the section which I have had taken at Roseberry, and is very 
puzzling and difficult to explain. Some other measurements 
and observations which I have recently made between the two 
points, while not explaining, appear to throw some light on 
the subject. 
At Cockshaw, about 1? miles south of Roseberry, the 
Pecten bed has become nearly all shale, with only two thin 
bands of ironstone ; below it is a band of 3 ft. 2 in. of shale. 
At Roseberry this same shale bed is split into two, differing 
quite distinctly from each other; or, as the section is not at 
present {very easy to explore, should it turn out that any of 
the shales above or below the two thin bands of ironstone at 
Cockshaw belong to the Pecten, then the difference between 
Roseberry and Cockshaw is, if anything, still more marked. 
Inside the mine at Roseberry, close to a fault, the whole 
character of the Pecten bed becomes altered; there are three 
thin bands of shale amounting in total thickness to only eight 
inches, and the ironstone bands have a total thickness of 3 ft. 
3 ins. Local variations evidently occur, shewing that the 
conditions existing at the time the strata were being formed 
must have been variable. Perhaps in this instance faulting 
and deposition and possibly denudation were progressing 
simultaneously, but the main point is that in distinctly local 
areas there are given variations in the character of the beds. 
Along the most southerly line of sections there are numerous 
local changes, but broadly speaking the ironstone in the main 
seam becomes less rich in iron and the impurities, chiefly 
silicia and alumina, become more pronounced as we proceed 
eastward. Along with this change there comes the cleaving of 
the ironstone into a top and bottom block, with a band of 
Dogger or shale between them, and just as in the converging 
line of sections on the coast, the band of shale thickens towards 
the east. 
Some of the local variations are curious. Thus in Spawood 
Mine, the Western side of the most southerly workings (ZL) 
shews a thicker band of shale and a thinner bottom block of 
ironstone than the eastern side (L2) 1,300 yards along the line 
Naturalist, 
