[en] Wave-number measurements were made on 10 uranium and 2 thorium transitions using the optogalvanic effect in a hollow-cathode discharge to position a single-frequency, cw dye laser to the peak of a transition. The wave number of the dye laser was measured by comparing it with the wave number of an iodine-stabilized He-Ne laser. The accuracy of the wave-number measurements was +-0.0006 cm^-₁. The data agree within +-0.002 cm^-₁ with previously reported uranium and thorium measurements whose estimated accuracy was +-0.003 cm^-₁