2S6 of the external senses.

It is becaufe the vifible object which covers anyother vifible objeft mtift always appear at leaftas large as that other objeft, that Opticians tellus that the fphere of our vifion appears to theeye always equally large; and that when we holdour hand before our eye in fuch a manner thatwe fee nothing but the infide of the hand, weltill fee precilely the fame number of viiible poin ts,the fphere of our vifion is Hill as completely filled,the retina is as entirely covered with the objectwhich is thus prefented to it, as when we furveythe moil extenfive horizon.

A young gentleman who was born with a cata-ra£t upon each of his eyes was, in one thoufandfeven hundred and twenty-eight, couched by Mr.Chefelden, and by that means for the firft timemade to fee diftinftly. “ At firft,” fays the opera-tor, “ he could bear but very little Sight, and“ the things he faw he thought extremely large;“ but upon feeing things larger, thofe firft feen“ he conceived lefs, never being able to imagine“ any lines beyond the bounds he faw; the room<£ he was in , he faid, he knew to be but part oft£ the houfe, yet he could not conceive that the“ whole houfe would look bigger.” It was una-voidable that he fhould at firft conceive, thatno vifible objeft could be greater, could prefentto his eye a greater number of vifible points, orcould more completely fill the comprehenfion ofthat organ, than the narroweft fphere of hisvi-lion. And when that fphere came to be enlarged,he ftill could not conceive that the vifible objetfts