438 DOMAIN V. CALCAREOUS. 



" But if the differences between the compact 

 and this kind are of little consequence, the geo- 

 logical differences are numerous and important. 



" This limestone is employed in architecture ; 

 the solidity of some of its varieties, and the ease 

 with which it is wrought, giving it great advan- 

 tages. It is called pierre de faille when it is in 

 large masses, and moellon when they do not ex- 

 ceed four cubic feet. 



" It is unequally dispersed, being rare in 

 England, and common in France, especially in 

 the environs of Paris, chiefly to the south of that 

 city, from Sevres to Gentilly. Its beds, which 

 are horizontal, extensive, thick, and continuous, 

 are situated between chalk, which it covers, as 

 may be observed at Meudon, and gypsum, 

 which covers it in some parts. It is separated 

 from the chalk by a bed of bluish potters' clay. 

 To different parts of its beds distinct names have 

 been applied, according to their quality, and 

 the uses for which they are destined. That 

 which is of a fine grain and compact texture is 

 called pierre de liais*: it may be cut in sharp 

 squares, and resists the weather; the thickness 

 of its beds seldom exceeds eight inches. The 



* In the eommon dictionaries, liais, and pierre de taille, are 

 translated freestone. Sandstone is gres. 



