MODE III. LIMESTONE. 441 



STRUCTURE II. CONCHITIC. 



Aspect 1. With nummulites, from Egypt. 



With ceriteSj from Paris. 



With various shells, from the vicinity of Bath. 



The pierre de tattle used at Marseilles is a con- 

 chitic limestone, of which the quarries are at Cape 

 Couronne *. 



MODE III. LIMESTONE. 



The characters of this rock will be given in 

 some distinct Structures. The combination, as 

 of the former Modes, is chiefly lime and car- 

 bonic acid, about 40 of the latter to 50 of the 

 former; whence the term carbonates of lime. Carbonates of 

 But the Modes differ in minute particulars, as 

 already mentioned. 



This useful rock abounds in most countries. 

 It is generally burnt to make lime and mortar; 

 but is also employed in building, and sometimes 

 in making roads, though the siliceous substances 

 be more durable and proper for the latter pur- 

 >ose. 



* Sauss. 1517. 



