The explanation of our power to see very thin, long objects at a very great distance, is not our affair, but is of importance because it serves to explain a number of similar phenomena spoken of by witnesses. We have either incorrectly to deny things we do not understand, or we have to accept a good deal that is deniable. We will start, therefore, with the well-known fact that a point seen for a considerable time may easily disappear from perception. This has been studied by Helmholtz and others, and he has shown how difficult it is to keep a point within the field of vision for only ten or twenty minutes. Aubert examines older studies of the matter and concludes that this disappearance or confusion of an object is peripheral, but that fixation of a small object is always difficult. If we fix a distant point it is disappearing at every instant so that an accurate perception is not possible; if however we fix upon a long, thin body, e.g., a wire, it is unnecessary to fix a single point and we may see the object with a wandering eye, hence more clearly. Helmholtz adds that weakly objective images disappear like a wet spot on warm tin, at the moment a single point is fixed, as does e.g., a landscape seen at night. This last acute observation is the basis of many a testimony concerning the sudden disappearance of an object at night. It has helped me in many an examination, and always to advantage. In this connection the over-estimation of the moon’s illuminating power is not to be forgotten. According to Helmholtz the power of the full moon is not more than that of a candle twelve feet away. And how much people claim to have seen by moonlight! Dr. Vincent[178] says that a man may be recognized during the first quarter at from two to six meters, at full moon at from seven to ten meters, and at the brightest full moon, an intimate may be recognized at from fifteen to sixteen meters. This is approximately correct and indicates how much moonlight is over-estimated.