366 Tbe H/Jlory of 



IX. A difficulty (till attending a balance fo fen- 

 fible is, (as then it muft be fenfible for the obfer- 

 vations*) that very few bodies can be weighed by 

 it ; for the moft either quite fink the balance un- 

 der water, or leave it quite a-float a- top, fo as not 

 to fink at all ; as, among all the above bodies, 

 fcarce ten have, barely of themfelves, fhewn their 

 degree of gravity. But this difficulty may be ea- 

 fily obviated, by correcting the levity and gravity, 

 by the adding and taking away of weights, and 

 then calculating how many degrees fuch weights 

 make out, and how much muft be added or de- 

 ducted. 



X. The fluid wherein you weigh muft be con- 

 ftantly one and the fame, alfo be of the fame de- 

 gree of warmth, or of cold ; whence, in winter, 

 the degrees appear not the fame as in fummer, even 

 though the very fame water be ufed. 



XI. The degrees on the above balance muft be 

 counted from below upwards, as thefe muft en» 

 creafe with the encreafe of gravity. 



XII. All the bodies you would weigh are pre- 

 vioufly, by tneans of a pencil, to be wetted with 

 water \ otherwife the air-bubbles adhering to the 

 body under the water, make it lighter than it is. 



XIII. Alfo all porous bodies, as crabs- eyes 9 

 chalk, &c. muft be fuffered to abforb their fill of 

 water ♦, elfe alfo the body proves lighter than it 

 really is. 



XIV. In regard to artificial, and other bodies, 

 care is alfo to be had, that they contain no in- 

 cluded 



