2 33 ) 



the eye is a mere window. It is a pane of 

 glafs itfelf, through which the imagination is 

 imprefled by the notices it receives of outward 

 objects j which notices, tho fometimes true, 

 are often falfe, particularly with regard to 

 the fize of objects j and will miflead it, unleis 

 corrected by experience. The mathematician 

 talks of the angle of vifion ; and demonftrates, 

 that the fize of the object in the eye muft be 

 in exact proportion to that part of the cone 

 of rays, which it intercepts : and it is on 

 this fuppofition, the painter afTerts, that an 

 extenfive diflance, exactly painted, tho in 

 miniature, will affect the fpectator like the 

 natural fcene. But many things are mathe- 

 matically true ; tho experimentally falfe. Such 

 is the famous puzzle of Achilles, and the 

 tortoife. The mathematician demonflrates, 

 that the tortoife muft win the race; tho not 

 one jockey at Newmarket would bet on his 

 fide. Jufl fo, the imagination revolts from 

 the mathematical account of vifion. If I ex- 

 amine, for inftance, the height of that tree, 

 by the fide of a notched flick, it is fcarce an 

 inch. But no mathematical proof can per- 

 fuade me, that I fee it under tbofe dimenfans. 



I am 



