The authors describe a small self-contained ultra violet recorder which they have built and used to measure the spectral output of lamps in accelerated weathering machines within the region 300 to 400 nm. The recorder took the place of a sample in the test machine and was used to measure xenon arc lamps and UV-emitting fluorescent tubes in terms of the horizontal distribution of radiation, rotationally integrated spectral distribution and the effect of different combinations of fluorescent tubes, and the deterioration in output of UV during the life of the lamps. From the results the authors suggest that by modification of the arrangement and selection of tubes a source could be developed with a spectrum more nearly matching the UV component in solar radiation. -- AATA