ON THE MANUFACTURE OF IRON. 743 
over which the deposit of ironstone, embraced within the title of this section, 
is found. Mr. John Marley, whose name has been, from the first, associated 
with its discovery in the neighbourhood of Middlesbro’, and who has devoted 
much attention to its geological position and extent, and the late Mr. Joseph 
Bewicke, to whom a long practical acquaintance with the subject gave abun- 
dant opportunity of studying this question, have both written on the subject 
at considerable length. To their works—the former in the Transactions of 
the Northern Institute of Mining Engineers, and the latter in a work on the 
Cleveland Ironstone—those persons who desire more detailed information are 
referred. 
It may be briefly stated, however, that Mr. Bewicke gives the dimensions 
of the field of ironstone as thirty miles by sixteen, from which he deducts 
sixty miles for denudation, giving a net area of 420 square miles. The 
brother and partner of the writer, Mr. John Bell, who possesses a very com- 
plete knowledge of the district, prepared models and maps of the country 
which agree pretty closely with these estimates. Mr. Bewicke roughly con- 
siders the yield to be 20,000 tons per acre, and hence infers that close on 
5000 million tons are contained in the Main Cleveland Seam, within the 
limits laid down*. We have already seen, in the preliminary account of this 
bed of ironstone, how varying in thickness it is. In some places, also, it 
becomes more or less split up by bands of shale, a circumstance which of 
course interferes greatly with its commercial value. Commencing with 
Grosmont, near Whitby, where it was first wrought in a systematic way, 
there are found two seams of ironstone, known as the Pecten and the Avicula 
bands. The former consists of 3 feet of ironstone, divided in the middle by 
a bed of shale 1} foot thick. Separated from this by 30 feet or more of 
shale is the other seam, the Avicula, embracing 44 feet of ironstone, along 
with 2 feet of shale ; and it is by these two bands uniting, as well as increas- 
ing in thickness, that we have further north the Main Cleveland Seam, as it 
is termed. In the northern portion of the field considerable irregularity in 
character is also observable. At Codhill the bed has an extended height, but 
is so interspersed with foreign matter that it is found necessary to confine the 
mining to a section of 53 feet; and the produce, from the circumstance of 
more or less shale bands running through the ironstone itself, is only about 
28 per cent. of metal. A little to the east of Codhill are the Belmont Mines, 
where the shales thin out, and in consequence the yield of iron is about 30 
per cent., the seam at the same time having increased in height to 7j feet. 
At Skelton, still further east, a marked improvement, both in thickness and 
in quality, is again discernible. The workings there are frequently 10 feet 
high, and a recent analysis of the entire section of stone gave above 36 per 
cent. of iron. The north side of the Vale of Guisbro’ is formed by an elevated 
ridge of land separating this valley from that of the Tees. At the western 
edge of this ridge are the Normanby mines, where the stone is worked at an 
average thickness of about 8 feet, containing 314 per cent. of iron. There is 
a general dip of the seam to the east from this point, and in its progress in 
that direction there is a gradual increase in thickness, and a little improve- 
ment in percentage of iron. It continues in this way past Eston and Up- 
~leatham, until it reaches Rockcliffe, where it attains a thickness of nearly 
* Tn an estimate recently made by the writer, based on the researches of Messrs. Hugh 
and T. J. Taylor, T. Y. Hall, &c., there would appear to be in our northern coal-field six 
thousand million tons of coal left for future use; so that there is just about fuel enough 
in the one district—reserving it for that purpose exclusively—to smelt the ironstone of 
the main seam of the other. 
