Fontenelle, of the Vfefulnefs 



been obferv'd with a Telefcope, nor ftudy'd. But 

 it is certain, that we had been considerable Loo- 

 fers by it : For thofe who have fome infight into 

 the Principles of Geography and Navigation know, 

 that fince thefe four Moons about Jupiter have 

 been difcover'd, they have been more ufeful to 

 thofe Sciences than our own Moon ; and that they 

 ferve, and {hall more and more ferve to make 

 new Sea-Charts, infinitely more exadfc than the 

 Old ; and are likely to fave the Lives of a vaft 

 many Seamen. Did we reap no other advantage 

 from Aftronomy than this from thefe Satellites of 

 Jupiter, that wou'd be fufficient to juftifie thofe 

 prodigious Calculations, thofe affiduous and nice 

 Obfervations, this great number of elaborate In- 

 ftruments, and this Noble Edifice built only for 

 this Science. However the greateft part of Man- 

 kind know nothing of thefe Satellites of Jupiter, 

 unlefs perhaps by hear- fay, and that too confu- 

 fedly ; or elfe they are ignorant of what Af- 

 finity they have with Navigation, or of the 

 great Improvements which have been lately 

 made in it. 



This is the Fate of Sciences, which are ftudy'd 

 and improv'd by few. Moft People are not fen- 

 fible of their Progrefs, and efpecially when made 

 in fome mean Callings. But what doth it figni- 

 fie, that we can now more eafily direct the Courfe 

 of Rivers, cut out Canals, and fettle new Navi- 

 gations j becaufe our Method of taking the Level 

 and making Sluces is infinitely better than here- 

 tofore ? Some Mafbns and Seamen have thereby 

 found their Bufinefs eafier, but they themfelvei 

 were not fen fible of the Skill of the Geometrician 

 who diie&ed them. They were mov'd, as the 

 Body by a Soul, it doth not know. Others are 



yet 



