A theoretical examination is made of convection, induced by applied thermal and solutal gradients inclined to the vertical, in a shallow horizontal layer of a saturated porous medium. The horizontal components of these gradients induce a Hadley circulation, which becomes unstable when the vertical components are sufficiently large. A linear stability analysis is carried out, and calculations are made using a low-order Galerkin approximation for the various modes of instability. The orientation of the preferred mode and the other critical quantities are determined for representative parameter values.