In a preliminary study the mean marginal error due to the edgeeffect of the old standard pyrheliometer ofK. Angstrom is found to be +2.4 per cent. A series of the new model A pyrheliometer designed at the Laboratory of the Swedish Meteorological and Hydrological Institute has given the same result concerning the discrepancy between the new model and the standard model of theK. Angstrom pyrheliometer. The new scale based on calculated constants of the A pyrheliometers without any marginal error gives one per cent higher values than the Smithsonian absolute scale of 1948. According to the Smithsonian Institution this remaining difference is due to an error in the A original and also in the new pyrheliometers, caused by a laterally reflected radiation on the back of the strips. This problem will be subjected to further experiments.