^8 M. Prevost on the shining of' the Eyes of the Cat, 



I am quite certain, that neither BufFon, nor Spallanzani, nor 

 M. Dessaignes, ever observed on purpose the shining of the eyes 

 of the cat, and that they never saw this phenomenon otherwise 

 than cursorily, as one sees when he does not attend to a thing, 

 or when one only partially attends to it ; otherwise, they would 

 immediately have perceived that the eyes of cats never shine in 

 intense darkness, and that it is sufficient for them to shine, that 

 too great a light does not prevent the pupil of the animal from 

 dilating much ; that, in reality, the phenomenon is only sensible 

 . to the observer, when his eye receives httle light from surround- 

 ing objects. 



The case, then, is the same with the eye which shines, as with 

 the light which the pictures of a panorama reflect, and which 

 appears to have all the intensity of that of the objects which they 

 represent, although much inferior to it. 



The less light the eye of the observer receives, the more is it sen- 

 sible to that which the eye of the cat projects, and the less need has 

 the latter of receiving any ; it must receive more to produce an 

 equal effect, if the former be situated in a lighter place. These 

 are the conditions of the phenomenon. They appear to me to 

 reduce this pretended phosphorescence to light reflected by a 

 shining object. I shall give two examples, which I select 

 Jrom among the best adapted to render me understood. 



1st, Ib a long and narrow passage, closed on all sides except- 

 ing the entrance, from which, during a very dark night, there 

 could come but little light, I saw the eyes of a cat shine. They 

 projected strongly upon the dark ground of a sort of deep nich, 

 which made them appear like burning coals. The light which 

 the eyes of the cat then received, and that which they sent back to 

 me, was without doubt very weak ; but to balance this, mine 

 not being affected by any other light, would necessarily be very 

 sensible to it. It was from a similar reason, that I once thought 

 I saw from my bed something which shone like a star of second 

 or third magnitude. It was nothing, however, but the back of 

 a chair not very well smoothed, which reflected some rays of the 

 moon ; but having at the time my head almost entirely enve- 

 loped in my covering, and my eyes receiving no other light, 

 these rays produced so much the more effect upon my retina, 

 that they arrived the more isolated at it. 



