From solar spectra obtained during the reentry of Calroc 4 the optical depth of the atmosphere in the wavelength interval 1213--1219 ¿ has been obtained for altitudes between ~120 and ~70 km. The data are consistent with the interpretation that molecular oxygen is the primary absorbing species under these conditions if the values of the O2 cross section in the 1216.2- to 1217.2-¿ region are approximately those of Ogawa (1968) and the O2 column densities in the 80-km region are approximately those derived from the 8-0 and 11-0 Schumann-Runge bands observed during the same flight.