This section is from the book "The Gardener V3", 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.
It is desirable to have the command of bottom-heat from hot-water pipes in a chamber underneath Pines, but it is also desirable to do with as little heat as possible from such means. Where 3 feet deep of good oak leaves and 9 or 10 inches of tan can be had there is not much need of heat from pipes, but it is well to be able to have such at command when the fermenting bed declines, as it does at certain seasons. We have known Pines to be very successfully grown for ten years in the same pit without anything further than an annual addition of about 8 inches of fresh tan mixed into the surface of the bed.