The apparatus consists of a coelostat and an infrared spectrometer coupled with an appropriate am plifier, mechanical rectifier and arecorder. The coelostat was constructed for use at stations of different geographical latitude. With this apparatus the emission spectra of the sun and the earth's atmosphere between 8 IJ. and 111J. wave-length were measured on clear days at different zenith angles of the sun and the percentage absorp tion and emission, respectively, of the atmospherical ozone layer were computed. Assuming the validity of the Lambert-Beer law the measured atmospherical...