^6 ESSAYS AND OBSERVATIONS 



Among beds of marie, a bed of coarfe 

 flone fometimes occurs. This flone, 

 however, I have generally found to contain 

 a confiderable proportion of calcarious 

 earth; but the quantity of this earth 

 •was too fmall to procure the ftone the 

 denomination of lime-ftone; and the 

 quantity of clay in it was not fufEcienc 

 to intitle it to a place among marles. 



SECT. IX. 



HAVING in this manner analyfed 

 marie as newly dug from the ground, 

 I next proceed to examine this fubftance 

 after its expofition to the air. The Ex- 

 periments 3. 4. 15. 16. 17. were repeated 

 upon marles that had been expofed for 

 many months. The events were the 

 fame, as when the experiments were made 

 upon newly dug marie ; nay, part of a 

 Jlratum of ftone-marle, after it had been 

 expofed for three years to the open air, 

 and had undergone all the vifible changes 

 that ufually proceed from fuch an expo- 

 fition, 



