Of THE EXTERNAL SENSES. 289

It has been laid, that no man ever law the samevihble object twice; and this, though, no doubt,an exaggeration, is, in reality, much lefs so thanat firft view it appears to be. Though I am aptto fancy that all the chairs and tables, and otherlittle pieces of furniture in the room where I amfitting, appear to my eye always the fame, yettheir appearance is in reality continually varying,not only according to every variation in their si-tuation and diftance with regard to where I am fit-ting, but according to every, even the moft insen-sible variation in the attitude of my body, in themovement of my head, or even in that of my eyes.The perspective necessarily varies according to all,even the fmalleft of these variations; and conse-quently the appearance of the objects which thatperspective presents to me. Observe what difficul-ty a portrait painter finds, in getting the personwho fits for his picture present to him preciselythat view of the countenance from which the firftoutline was drawn. The painter is scarce evercompletely satisfied with the situation of the facewhich is presented to him, and finds that it isscarcely ever precisely the fame with that fromwhich he rapidly sketched the firft outline. Heendeavours, as well as he can, to correct the dif-ference from memory, from fancy, and from afort of art of approximation , by which he strivesto express as nearly as he can, the ordinary effeflof the look, air, and character of the person whosepifture he is drawing. The person who drawsfrom a ftatue, which is altogether immoveable,