back of the head. With the 14 MeV neutron beam, however, LF were reported. Lasting for short periods of time, "streaks" were reported when the beam entered one eye from the front. The "streaks" seen had varying lengths (a maximum of 2 degrees of visual angle), and were seen to either have a blueish-white color or be colorless. All but one observer reported seeing fainter but a higher number of "points" or short lines in the center of visual field. When the beam entered both eyes in a lateral orientation, the number of streaks reported increased. The orientation of the streaks corresponded to the orientation of the beam entering the eye. Unlike in the previous case, the streaks seen were more abundant in the periphery than the center of visual field. Lastly, when the beam entered the back of the head, only one person reported seeing the LF. From these results, the researchers concluded that at least for the LF seen in this case, the flashes could not be due to Cherenkov radiation effects in the eye itself (although they did not rule out the possibility that the Cherenkov radiation explanation was applicable to the case of the astronauts). They also suggested that because the number of LF observed decreased significantly when the beam entered the back of the head, the LF were likely not caused by the visual cortex being directly stimulated as this decrease suggested that the beam was weakened as it passed through the skull and brain before reaching the retina. The most probable explanation proposed was that the LF were a result of the receptors on the retina being directly stimulated and "turned on" by a particle in the beam. In another experiment, Tobias et al. (1971) exposed two people to a beam composed of neutrons ranging from 20 to 640 MeV after they were fully dark-adapted. One observer, who was given four exposures ranging in duration from one to 3.5 seconds, observed "pinpoint" flashes. The observer described them as being similar to "luminous balls seen in fireworks, with initial tails fuzzy and heads like tiny stars". The other observer who was given one exposure lasting three seconds long, reported seeing 25 to 50 "bright discrete light, he described as stars, blue-white in color, coming towards him". Based on these results, the researchers, like in Charman et al. (1971), concluded that while the Cherenkov effect may