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

 glafs itfelf, through which the imagination is 

 imprelTed by the notices it receives of outward 

 objedts; which notices, tho fometimes true, 

 are often falfe, particularly with regard to 

 the lize of objeds ; and will miilead it, unlefs 

 corredted by experience. The mathematician 

 talks of the angle of vifion ; and demonftrates, 

 that the fize of the objedt in the eye mufl be 

 in exadt proportion to that part of the cone 

 of rays, which it intercepts : and it is on 

 this fuppofition, the painter afTerts, that an 

 extenfive diftance, exadlly painted, tho in 

 miniature, will aiFedl the fpedtator hke 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 demonftrates, 

 that the tortoife miifi win the race ; tho not 

 one jockey at Newmarket would bet on his 

 fide. Juft 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 ftick, it is fcarce an 

 inch. But no mathematical proof can per- 

 fuade me, that I fee it wider thofe dmetijions. 



I am 



