194 Burton: The Cleveland Ironstone. 
gave the total quantity of workable stone in the main seam as 
685,650,000 tons. 
I have been at some trouble to make an independent esti- 
mate and I arrive at figures very closely agreeing with those of 
Mr. Barrow. According to my calculation the total area of 
workable stone in the main seam is 43°48 square miles, or 27,827 
acres. The sp. g. is 2°86* which gives 3,467°89 tons per acre 
for every foot in thickness. Taking the average thickness of 
stone at seven feet, this gives 24,275°3 toms per acre. 27,827 
acres by 24,275 tons gives 675,500,425, differing only from Mr. 
Barrow by about 10,000,000 tons. From the quantity thus 
ascertained must be deducted waste in winning, which will 
approximate 10 per cent. and leave the available quantity 
607,950,383 tons, of which there has already been won about 
270,000,000 tons, leaving unworked about 338,000,000 tons, 
which at 6,000,000 tons per year will last 56 years. 
This leaves out of account the top seam, the Pecten seam, 
and the two foot seam, which together probably contain more 
‘stone than the main seam. It is all a question of cost whether 
they enter the field against imported ores or remain where: 
they are for the edification of a future race of geologists. 
The seams over considerable areas are full of local faults, 
and there are some of greater magnitude. The dips are vari- 
able, but the highest position above sea level is in the west. 
At Eston the outcrop is about 300 feet above sea level with a 
dip of 3 inches to the yard. At Roseberry it is about 750 
feet above sea level with a gentle dip to the south-east. At 
Stanghow south it is 151 feet above sea level, with a dip of 
.815 inches per yard south-east. At Liverton south the seam 
is 218 feet below sea level. 
The percentage of iron in the stone is fairly constant in 
given areas (although as already said, it gets decidedly worse 
eastward and southward), but it is very variable in distribution 
throughout the mass. 
According to Dr. Stead, the porosity of the Raw Ironstone is 
22 per cent. of the actual volume. From this one may con- 
clude that there must have been a considerable amount of 
carbonate of lime dissolved and carried away in solution 
subsequent to the conversion of the major portion of the original 
limestone rock into carbonate of iron, as the shrinkage from 
substitution is insufficient to account for such a high porosity. 
My thanks are due and heartily tendered to Dr. Stead 
for the loan of the blocks on Plates VIII.-X., and to the Mines’ 
Managers who have kindly supplied me with the latest facts 
which have enabled me to prepare sections of the main seam 
up-to-date. t 
+ Wide Dre eee ssuead: 
Naturalist, 
