OYSTERS, CLAMS, AND OTHER MOLLUSKS 241 



secondary "set" oysters. Other shells, rocks, stakes, 

 or even brush would answer this purpose, but, since 

 most oystermen have a surplus of oyster shells, these 

 are usually spread on the bottom selected for the 

 new ground. Another use of great importance is as 

 grit for poultry. Both oyster and egg shells consist 

 largely of calcium carbonate. Chickens and other 

 domestic birds have difficulty in obtaining sufficient 

 calcium to form shells for their eggs. In order to 

 aid the birds to get an ample supply of this element, 

 poultrymen feed cracked oyster shells to them. Shells 

 are prepared for cracking by drying in a rotary 

 drier, and are then crushed and screened into various 

 sizes of grits. Oyster shells are also made into lime 

 by strongly heating in a kiln. This process, called 

 burning, destroys the organic matter of the shell 

 and converts the carbonate of lime into the oxide. 

 Lime prepared in this way is used for plaster, fer- 

 tilizer, and the like. Formerly many oyster shells 

 were used in the construction of roads, the well 

 known shell roads of the South being built of this 

 material. Superior road materials are now available, 

 so that oyster shells are used less and less for this 

 purpose. 



The American Clam Industry 

 Long before the arrival of the first white man in 

 America, clams were the favorite food of the Indians 

 along the coasts. The sites of the old Indian villages 

 are still well defined by huge piles of clam shells, or 

 kitchen-middens, as they are called. Clams were not 

 only a source of food but also of "suckawhock," 

 or black money. Wampun or white money was also a 



