ALLUVIA. 633 



SECOND SUBDIVISION. 



Compound. 



A. Substances of various kinds and sizes ce- 

 mented by carbonat of lime. 



a. Quartz sand cemented in this manner. 



On seashores and in river alluvia. Abounds 

 on the shores of the Messina, where it is wrought 

 for O3conomical purposes. Occurs under singu- 

 lar modifications near Delvin in Perthshire. 



b. Fragments of many kinds cemented in 



the same way into a solid mass. 



On the north coast of Cornwall, near Dunbar, 

 in Rasay, and on other sea shores. 



B. Various substances cemented by rust of iron. 



a. Quartz, sand, and gravel: recent ferru- 

 ginous sandstone. Resembles the 

 hard portions of the ferruginous sand 

 deposits of the English strata, 

 b. Flint gravel, clay, and sand, united by 

 the same means. 



Occurs near Croydon, and elsewhere, in the 

 gravel bed. 



Some of the trap rocks seem to undergo a 

 similar process after disintegration ; forming a 

 recent tufa. 



The English puddingstones, so well known, 



