A diagram consisting of a section of a span-roofed pit. These pits are useful for plant culture. A, Ordinary Soil; b, Passage; c, Heated Chambers; d, Plunging Beds; e, Hot-Water Pipes.

Section of Span-Roofed Pit

A diagram consisting of a section of a span-roofed pit. These pits are useful for plant culture. A,…