O F F S S I L S. 



S LXXIV. Primitive Earths.. 



CRONSTEDT has eftablifhed nine primitive 

 earths, but accurate experiments have lincc 

 flicwn that the greater number of them were 

 compounded, fo that the account is reduced to 

 three only; the calcareous, iiliccous, and argilla- 

 ceous. We have however to add new earths, with 

 which he was not acquainted, the terra pon.dc- 

 rofa and ma^ncfia. We reckon therefore live 

 primitive earths. 



LXXV. Of the common Origin of Earths. 



ALTHOUGH the powers of chcmiflry have not 

 yet been able to decompofe thefe five earths, 

 the reduction of them all to one fpecies, or, 

 at lead, to a fmallcr number than the prefent, 

 may pofTibly be the reward of future induftry. 

 I acknowledge myfcjf of this opinion, and I 

 think with fonic foundation. Clay, for exam- 

 ple, is nothing elfe than calcareous earth, fo 

 Ariclly combined with fomc unknown acid, that 

 the fcpuration of them has hitherto been attempt- 

 ed in vain. No one certainly could have fuf- 

 peclcdthe calcareous bafe in the lapis pwhlerofus, 

 which has been dtmonil rated by amilytis. In 

 like manner, other fubftanccsmay be invcfiigat- 

 ed. But until proper experiments ihall have ful- 

 ly developed the nature of fuch compolitions, 



