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but not foluble in pure water, ductile while 

 moift, not inflammable. 



a. There are feveral kinds of molds which 

 are principally diftinguifhed~ by their colors. 

 Common mold, covers generally the furface 

 of the globe ; does not effervefce with acids, 

 nor is it convertible into quicklime. 



b. Clays, mixed with a quantity of water, form 

 a ductile pafte ; in the fire they harden. 



Thefe are various in their confidence and 

 color, owing to their mixture with other bodies. 

 Some, containing calcareous fubftances, effer- 

 vefce with acids, which they do not when 

 pure^ and their variety in color is owing to 

 the addition of iron, or other minerals. They 

 are diftinguifhed into porcelain clay, potter's or 

 pipe-clay, common clay, boles, ochres, fuller's 

 earth, tripela or rotten ftone, loam, &c. 



jc. Chalks and marles are frequently calcareous 

 and effervefce with acids whence they have 

 been claffed under calcareous ftones but as 

 their confidence is different, and their effects 

 with acids various, they are here placed under 

 the divifion of earths (c). 



B. Calcareous stones effervefce with, and are 

 diffolved by acids ; convertible into quicklime 

 by burning \ and do not ftrike fire with fteel. 



a. They appear under many different forms, 

 and are found in ftrata in the bowels of the 

 earth, and frequently jn large beds, as lime- 

 ftone, marble, &c. 



b. Some ftones, which in their flructure, ap- 

 pearance, and chemical properties refembie 



U) Vide Da Cofta's Natural Hiflory qf Foffils, page 

 §j and 75? 



marble, 



