ANALYSIS OF LITHOMARGE. 171 



vapour is replaced by an equal quantity, the 

 whole folution immediately becomes turbid, and 

 the argillaceous earth exactly faturated, falls to 

 the bottom. This procefs, however, is liable 

 to objection : For as the vitriolatcd zinc alfo re- 

 quires an exccfs of acid, the proper criterion for 

 regulating the operation is yet to be afccrtain- 

 cd. 



From what then has been faid, we may con- 

 clude, that a centenary of Lcmnian earth con- 

 tains 47 parts of filiceous earth, 5.4 of aerated 

 calcareous earth, 6.2 of aerated magncfia, 10 

 of argillaceous earth, 5.4 of calcined iron, and 

 17 of a moill volatile fubltancc. The fum of 

 the experiments taken fcparatcly, amounts to 

 102 ; but this fmall excels is owing to the diffi- 

 culty of rendering the argillaceous earth pcr- 

 dr. 



5 in. Of tbc Ofmundlc Earth, 



Tins earth is the produce of Mount Oihuind, 

 in the parilh of Rattvik, in ail Dalecarlia, 

 where it forms a flratum of three feet thick. 

 The rock of the mountain is calcareous, hard, 

 and interfered with ftrata of argillaceous mat- 

 ter and fchiilus. Petroleum is found in fcvcral 

 places of it, but efpecially in the fchiftus. But 

 a more particular dcfcription and delineation of 



the 



