Photoelectric observations are described, intended to detect or set an upper limit to anomalous absorption in the violet wing of the solai K line following flares. Such absorption would be direct evidence of a cloud of approaching particles, the presumed source of great geomagnetic storms. During 1949–50 numerous photoelectric observations failed to reveal in most cases any absorption exceeding 0·5 per cent, corresponding to particles with approach velocities between 650 km/sec and 1500 km/sec, for several hours after flares, even when followed by magnetic disturbance. A few cases of doubtful effects up to one per cent are noted. Since the strongest absorption would be expected shortly after expulsion, the negative results imply a low abundance of Ca II ions in the cloud. This has been suggested by theoretical work, though in conflict with earlier photographic observations of absorption during magnetic storms