POPULAR FALLACIES. 



near the horizon the mind is impressed with the idea that the 

 distance of these objects is much greater than when on the 

 meridian, and that their apparent magnitude being the same,, 

 the real magnitude is judged to be greater in the same propor- 

 tion as the distance is supposed to be greater. Thus, if we are 

 impressed with the notion that the sun seen in the horizon i^:- 

 twice as distant as the sun seen in the meridian, we shall infer 

 its diameter to be twice as great, since it appears the same ; and 

 if its diameter is twice as great, its apparent superficial magnitude 

 will be four times as great. 



The operations of the judgment in such cases are so rapid, 

 and the effect of habit is such, that we are altogether uncon- 

 scious of them. A thousand examples might be given of bodily 

 actions and motions performed by the dictates of the will, of 

 which we retain no consciousness. It is difficult in the case we 

 have just explained, for minds unaccustomed to metaphysical) 

 inquiries, to satisfy themselves of the validity of the explanations 

 we have given. Yet, if it be remembered that it is capable of 

 unequivocal proof that the illusion is not optical, and that, in 

 fact the apparent magnitudes of the moon on the horizon and 

 the meridian are not different, it will easily follow that the erro* 

 must be mental, and the only explanation which has ever beer-, 

 given of it is that which we have here offered. 



There is perhaps no sense which more requires the vigilant 

 exercise of the understanding to rectify its impressions, thai* 

 that of sight. The susceptibility of the organ of vision itself IF 

 liable to frequent and rapid change, and the same objects at 

 different times produce upon it extremely different impressions, 

 A situation in which, in one condition of the eye, we shalS 

 appear to be in absolute darkness, will present to us, in another 

 state of the organ, sufficient light to render visible the objects 

 around us. If we are suddenly deprived of the illumination 6? 

 any strong artificial light, we appear to be for the moment in 

 absolute darkness ; but when the organ of vision has had time 

 to recover itself, we often find that there is sufficient light to 

 guide us. 



" Thus when the lamp that lighted 

 The traveller at first goes out, 

 He feels awhile benighted, 



And lingers on in fear and doubt. 



"But soon, the prospect clearing, 



In cloudless starlight on he treads, 

 And finds no lamp so cheering 



As that light which heaven sheds." MOOHE. 



4. The mechanism which the all-wise Creator that made the eyf 

 84 



