19« THE PHILOSOPHT 



The fenfe of feeing, without the aid of experience, con- 

 veys no idea of diftance. If not affifted by the fenfe of 

 touching, all objefls would feem to be in contact with the eye 

 itfelf. Objedls appear larger or fmaller according as they 

 approach or recede from the eye, or according to the angle 

 tliey fubtend. A fly, when very near the eye, feems to be 

 larger than a horfe or an ox at a diftance. Children can 

 have no idea of the relative magnitude of objefls, becaufe 

 they have no notion of the different diftances at which they 

 are feen. It is only after mealuring fpace by extending the 

 hand, or by tranfporting their bodies from one place to anoth- 

 er, that children acquire juft ideas concerning the real dif- 

 tances and magnitudes of obje(ri:s. Their ideas of magnitude 

 refult entirely from the angle formed by the extreme rays re- 

 flected from the fuperior and inferior parts of the objedl : 

 Hence every near obje£l muft appear to be large, and every 

 diflant one fmall. But after, by touch, having acquired 

 ideas of diftances, the judgment concerning magnitude be- 

 gins to be re£lified. If we judge folely by the eye, and have 

 not acquired the habit of confidering the fame objects to be 

 equally large, though feen at different diftances, the nearefl 

 of two men, though of equal fize, would feem to be many 

 times larger than the fartheft. But we know that the lafl 

 man is equally large with the firft ; and, therefore, we judge 

 him to be of the fame dimenfions. Any diftance ceafes to 

 be familiar to us, when the interval is vertical, inftead of be- 

 ing horizontal *, becaufe all the experiments by which we 

 ufually rectify the errors of vifion, with regard to diftances, 

 are made horizontally. We have not the habit of judging 

 concerning the magnitude of objects which are much elevat- 

 ed above or funk below us. This is the reafon that, when 

 viewing men from the top of a tower, or when looking up 

 to a globe or a cock on the top of a fteeple, we think thefe 

 objects much fmaller than when feen at equal diftances in a 



