Microscopic and macroscopic descriptions are given of the process of drying from a long porous and permeable column, initially saturated fully with a liquid which wets its grains. A comparison is made with the process of drainage, and it is shown that the “first stage of drying” corresponds with the extension down into the pack of a saturation profile derived from the capillary pressure curve. In the second stage of drying this profile penetrates still deeper; its upper end coincides with a “bone dry front,” the progress of which down the pack is controlled by diffusion of vapor to the surface. Results of the analysis are compared to measurements of front position during the drying of unconsolidated fluorite packs.