630 ALLUVIA. 



composition of animals and vege- 

 tables : mud. In many estuaries, 

 and in the deposits of slow moving 

 rivers. 



D. Consisting principally of calcareous matter. 

 Marie. 



a. Powdery, or imperfectly plastic, with 



few or no distinct fragments of shells: 

 often much mixed with sand and clay. 



b. A congeries of shells and fragments of 



shells, more or less pure. Shell 

 marie of agriculturists. 



Those which contain organic remains, are 

 found on sea shores, or on lands that have been 

 deserted by the sea, as well as in lakes, where 

 they often accompany peat. Where found in dry 

 places inland, they generally mark the situations 

 of antient lakes. But, in several parts of Perth- 

 shire, they also occur on declivities, having been 

 formed by terrestrial shells. In other cases, they 

 are formed by the alluvia of calcareous rocks. 



E. Of fine materials, and loose, or incompact. 



a. Quartz sand. 



On sea shores, and also removed by the 

 winds, so as to form sand hills and other similar 

 inland deposits, which are consolidated by the 

 growth of vegetables, and sometimes by the for- 



