III. Estimate of Quantity.

The ironstone being in many places of so open a structure that it would be useless to take the specific gravity of a number of samples with a view to finding that of the whole, I have assumed this to be 2.8; thus making a cubic foot weigh 175 lb.

I was unable to do more than take a number of aneroid readings, and so estimate the height of the main hill: this appears to be about 200 feet. Acting page 57 on these assumptions, I have made the following calculations:—

A.	Average height	200 feet
	Average width	950 feet
	Average section 119,700 square ft., but deducting one-third for gullies, this becomes 79,800 sq. ft.
	Length	8,316 feet
	No. of tons of hematite	51,835,600
B.	Average height	34 feet
	Average section	5,100 sq. feet
	Length	2,100 feet
	No. of tons of hematite	836,719
C.	Average height	14 feet
	Diameter	310 feet
	No. of tons of hematite	82,553
D.	Average height	10 feet
	Diameter	75 feet
	No. of tons of hematite	3,450
E.	Average height	10 feet
	Diameter	75 feet
	No. of tons of hematite	3,450
F.	Average height	20 feet
	Diameter	240 feet
	No. of tons of hematite	70,686
G.	Average height	20 feet
	Diameter	90 feet
	No. of tons of hematite	9,927
H.	Average height	20 feet
	Diameter	120 feet
	No. of tons of hematite	13,254
I.	Average height	50 feet
	Diameter	132 feet
	No. of tons of hematite	37,419
	Total No. of tons of hematite	52,893,058

In this estimate no ore lying outside the boundary-line is included, nor are the deposits at K and L.

This shows that the mass of the hill is clay, with merely a shell of hematite. From this fact I am doubtful as to whether this may not occur in a good many cases; but it could be proved only by boring.

Without this aid no accurate estimate of the quantity of hematite can be made.