OF NATURAL HISTORY, 185 



is only after meafuring fpace by extending the hand, or by tranf- 

 porting their bodies from one place to another, that children acquire 

 jufi; ideas concerning the real diflances and magnitudes of objed:Si 

 Their ideas of magnitude refult entirely from the angle formed by 

 the extreme rays reflefled from the fuperior and inferior parts of 

 the objed : Hence every near objeifl mud appear to be large, and 

 every diftant one fmall. But after, by touch, having acquired ideas 

 of diftances, the judgment concerning magnitude begins to be redi- 

 fied. If we judge folcly by the eye, and have not acquired the ha- 

 bit of confidering the fame objedls to be equally large, though feen 

 at different diftances, the neareft of two men, though of equal fize, 

 would feem to be many times larger than the fartheft. But we 

 know that the laft man is equally large with the firft ; and, there- 

 fore, we judge him to be of the fame dimenfions. Any diftance 

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

 being horizontal; becaufe all the experimfnts by which we ufually 

 redify the errors of vifion, with regard to diftances, are made hori- 

 zontally. We have not the habit of judging concerning the mag- 

 nitude of objeils which are much elevated 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 objeds much fmaller than when feen at equal diftances 

 in a horizontal diredion. During the night, on account of the dark- 

 nefs, we have no proper idea of diftance, and, of courfe, jud^e of 

 the magnitude of objeds folely by the largenefs of the angle or 

 image formed in the eye, which neceffarily produces a variety of 

 deceptions. When travelling in the night, we are liable to miftake 

 a bufh that is near us for a tree at a diftance, or a diftant tree for a 

 bufli which is at hand. When benighted in a part of the country 

 with which we are unacquainted, and, of courfe, unable to 

 judge of the diftance and figure of objeds, we are every moment 

 liable to all the deceptions of vilion. This is the origin of that dread 

 t A a . which 



