OF SOLIDS AND I IQUIDS. 243 



medium which is filled by the whole of the at- 

 mosphere, and the atmosphere ought to form 

 the nucleus of the earth itself. 



As bodies of equal bulk, lose as much of 

 their weight, as is equal to the bulk of the 

 matter which they have displaced; it is very 

 apparent, that bodies of unequal densities, and 

 of the same bulks, will not be equiponderant 

 in one aiid the same medium. That when the 

 medium is rarer than the bodies which are 

 placed in it, the denser bodies will weigh 

 more than the rarer ones ; and, on the contrary, 

 when they are placed in media of greater rarity 

 than themselves, the body of the greatest magni- 

 tude will acquire a greater quantity of weight 

 than the smaller one ; thus it is that different 

 masses of copper, and of gold, which were ba- 

 lanced in water, will be found to weigh very 

 unequally in air ; and if a piece of cork, and a 

 piece of lead, were balanced in water, it will 

 be found that the cork will acquire a greater 

 increase of weight than the lead ; and that the 

 weight of both will increase in proportion as 

 the density of the medium decreases; con- 

 sequently, that all bodies are lighter nearer the 

 surface of the earth, and heavier in the upper- 

 most part of the firmament. It is, therefore, 

 not only not true, that all bodies are mutually 

 heavy, but I contend, that instead of the gra- 

 vity, or the weight, of bodies increasing, in pro- 



R2 



