This section is from the book "The Gardener V2", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
The report of Messrs Gledhill & Hamerton sets all doubt at rest as to the unlimited abundance of iron-sand at Taranaki. On arriving at the east bank of the Henni river, they proceeded to dig at several places, with the following results: In the space situated between the sandhills and high-water mark they found solid iron-sand to the depth of 4 feet, and no apparent change at that depth. Previous experiments afford grounds for the belief that the deposit of iron-sand varies from 15 to 30 feet in depth.