  Gravitational potentials which change in time induce fluctuations in the
observed cosmic microwave background (CMB) temperature. Cosmological structure
moving transverse to our line of sight provides a specific example known as the
moving lens effect. Here we explore how the observed CMB temperature
fluctuations combined with the observed matter over-density can be used to
infer the transverse velocity of cosmological structure on large scales. We
show that near-future CMB surveys and galaxy surveys will have the statistical
power to make a first detection of the moving lens effect, and we discuss
applications for the reconstructed transverse velocity.
