A user-friendly introduction to convection in porous media, such as fibrous insulation, geological strata, and catalytic reactors. This is a self-contained presentation, requiring only routine classical mathematics and the basic elements of fluid mechanics and heat transfer. It will thus be of use not only to researchers and practising engineers as a review and reference, but also to graduates and others just entering the field. Applications discussed include such disparate topics as building insulation, energy storage, nuclear-waste disposal, coal and grain storage, chemical reactor engineering, groundwater flow, and stability of snow to avalanches. In this second edition the authors have added: discussions of compact heat exchangers and of tree networks; new material on external natural convection; descriptions of the effects of magnetic fields, of rotations, and of periodic heating; discussions of inclined gradients and of the solidification of alloys; and an extensive treatment of two-phase flows. An extensive list of references -- emphasising recent experimental work -- provides access to the current research literature.