THE PERCEPTION OF THINGS. 10 1 



hear,' said the friend, ' the noise of a hunt on the mountain?' M. van 

 Beneden listens and distinguishes in fact the giving-longueof the dogs. 

 They listen some time, expecting from one moment to another to see a 

 deer bound by; but the voice of the dogs seems neither to recede nor 

 approach. At last a countryman comes by, and they ask him who it is 

 that can be hunting at this late hour. But he, pointing to some puddles 

 of water near their feet, replies: 'Yonder little animals are what you 

 hear. ' And there there were in fact a number of toads of the species 

 Bombinator igneus. . . . This batrachian emits at the pairing season a 

 silvery or rather crystalline note. . . . Sad and pure, it is a voice in 

 nowise resembling that of hounds giving chase." * 



The sense of sight, as we have seen in studying Space, 

 is pregnant with illusions of both the types considered. 

 No sense gives such fluctuating impressions of the same 

 object as sight does. With no sense are we so apt to treat 

 the sensations immediately given as mere signs ; with none 

 is the invocation from memory of a thing, and the conse- 

 quent perception of the latter, so immediate. The ' thing ' 

 which we perceive always resembles, as we have seen, the 

 object of some absent sensation, usually another optical 

 figure which in our mind has come to be the standard of 

 reality ; and it is this incessant reduction of our optical 

 objects to more * real ' forms which has led some authors 

 into the mistake of thinking that the sensations which 

 first apprehend them are originally and natively of no 

 from at alLf 



Of accidental and occasional illusions of sight many 

 amusing examples might be given. Two will suffice. One 

 is a reminiscence of my own. I was lying in my berth in 

 a steamer listening to the sailors holystone the deck out- 

 side ; when, on turning my eyes to the window, I perceived 

 wdtli perfect distinctness that the chief-engineer of the ves- 

 sel had entered my state-room, and was standing looking 

 through the window at the men at work upon the guards. 

 Surprised at his intrusion, and also at his iutentness and 



* Examen Critique de la Loi Psychophysique (1883), p. 61. 



f Compare A. W Volkmanu's essay ' Ueber Ursprungliches und Erwor- 

 benes in den Raumanschauungen,' on p. 139 of bis Untersuchungeu im 

 Gebiete der Optik ; and Chapter xni of Hering's contribution to Her- 

 mann's Handbuch der Physiologie, vol. iii. 



