4 Williamson (Physic. Rev., 21, 110, 1923), using a tartaric acid solution composed of 64 parts of water to 1 of saturated solution in an absorption cell 3.2 cm. in length, found no transmission below 2450 A. Using a 3 mm. layer of 1.7% solution we found with a quartz spectrograph no transmission below 2340 A. Moreover, through even a 0.17% solution, 'we obtained no unsensitized ozone formation...