OF THE EXTERNAL SENSES. 263

as preffing upon the organ, but as in the organ.What we fed while we hand in the funfhine du-ring a hot, or in the fhade during a frofly, day,is evidently felt, not as prelling upon the body,but as in the body. It does not necefiarily fug-geft the prefence of any external object, nor couldwe from thence alone infer the exiflence of anyfuch objed. It is a fenfation which neither doesnor can exift any where but either in the organwhich feels it, or in the unknown principle of per-ception , whatever that may be, which feels inthat organ, or by means of that organ. Whenwe lay our hand upon a table, which is eitherheated or cooled a good deal beyond the adtualtemperature of our hand, we have two diflindlperceptions: firft, that of the folid or refilling ta-ble, which is necefiarily felt as fomething externalto, and independent of, the hand which feels it:and fecondly, that of the heat or cold , which bythe contact of the table is excited in our hand,and which is naturally felt as nowhere but in ourhand, or in the principle of perception which feelsin our hand.

But though the fenfations of heat and cold donot neceffarily fuggefl the prefence of any exter-nal objeft, we foon learn from experience thatthey are commonly excited by fome fuch object;fometimes by the temperature of fome externalbody immediately in contact with our own body,and fometimes by fame body at either a moderateor a great diftance from us; as by the fire in achamber, or by the fun in a Summer’s day. By