NATURAL HISTORY. 99 



and an extensive prospect. With this he seemed great- 

 ly charmed ; and the landscape before him he called a 

 new method of seeing. He was couched in the other 

 eye, a year after, and of hoth operations the success 

 was equal. AVhen he saw with both eyes every thing 

 appeared to him twice as big as when he saw but with 

 one, although he did not see double, or at least he dis- 

 covered no marks from which any such conclusion 

 could be inferred. 



Distance is only conceived by experience, for the 

 tr.ore distant an object is, the less it appears. When, 

 from certain circumstances, we cannot form a just con- 

 ception of distance, and when we cannot judge of ob- 

 jects but by the angle, or rather by the image, which 

 they have in our eyes, we are then necessarily deceived 

 as to their size. Every man has felt, how liable we are 

 in travelling by night to mistake a bush which is near 

 for a tree at a distance, or indeed a distant tree for a 

 bush at hand. In the same manner if we do not dis- 

 tinguish objects by their shape, and if we cannot by it 

 judge of distance, the same fallacy will still continue. 

 Jn this case, a fly, which may pass before us with 

 rapidity, will seem to be a bird at a considerable dis- 

 tance ; and a horse which may be in the middle of a 

 plain, not moving, and in an attitude similar, for in- 

 stance, to that of a sheep, will seem to be no bigger 

 than a sheep, till we have found out that it is a horse. 



If, therefore, we are benighted in a strange place, 

 where no judgment can be formed of distance, we are 

 every moment liable to deceptions of vision. Hence 

 originate the dreadful stories of spectres, and of those 

 wonderful, hideous, and gigantic figures, which so 

 many persons speak of having seen. Though such 

 figures, it is commonly asserted, exist solely in the iaui- 



