ADVERTISEMENT. XlX 



îheîr diftance from the North, or to the Eaft. 

 Their Latitude gives one complete circle, and their 

 Longitude another ; but the interfedion of thefe 

 two meafurements determines precifely the place 

 where they are. We are capable of afcertaining 

 truth, in like manner, only by confidering it under 

 a variety of relations. For this reafon it is, that 

 an objeâ: which it is in our power to fubjed to the 

 examination of all our fenfes, is much better 

 known to us than an objed to which we can apply 

 the teft of but one. Thus, we have a much more 

 exad knowledge of a tree than of a ftar, becaufe 

 we both fee and touch the tree : the flower of the 

 tree affords us dill more knowledge of it than the 

 trunk, becaufe we can farther apply to it the teft 

 of fmelling; and finally, our obfervations multiply, 

 when we examine it by the fruit, becaufe we can 

 now call in the evidence of the tafte, and have the 

 combined information of four fenfes at once. As 

 to objeâ:s toward which we are able to diréâ: but 

 one of our organs, fiy that of vifion, we can ac- 

 quire the knowledge of thefe only by confidering 

 them under difi^erent afpefts. That tower in the 

 horizon, you fay, is blue, fmall and round. Yoii 

 approach it, and find it to be white, lofty and an-» 

 gular. Upon this you conclude it to be fquare ; 

 but on walking round it, you fee that it is pen- 

 tagonal. You judge it to be impoffible to afcer- 

 tain it's height without the help of an inftrument, 



b 2 for 



