fome ufe and fcrvicc to the inquifitivc and philofo- 
phicai part of the world. As I perfuade my (elf they 
really will, when they (hall be further rc&ificd, by the 
omiffton of the erroneous or uncertain experiments ; 
when they (hall be enlarged by the addition of fuch 
, others, as may ftill be found in good authors, or 
which yet remain unpublilhed in the clofets of the 
curious: and cfpecially if fome fuch gentlemen as 
have skill, leifurc, and opportunities, (hall pleafe 
to fupply their remaining dcfc&s, by the com- 
munication of their own obfervations, made upon 
thole bodies, whofe fpecific gravities have not as yet 
been carefully recorded. 
Denique cur alias aliis pr a ft are vpdemus 
Ponder e res rebus , nihilo major e figura ? 
Nam, ft tantundem eft in Lana glomere , quantum 
Corporis in Plumboft, tantundum pender e par eft. 
Lucret. 
