BULLETIN 15 6, UNITED STATES NATIONAL MUSEUM 



The study of the methods of construction of the walls of a vessel 

 has for purposes of comparison less value than a study of the surface 

 finish, for the reason that coiling methods were widely extended in 

 America and in Africa from ancient times. If we were forced to 

 rely alone on methods of wall construction, that is, whether coiled or 

 cut from the solid, it would be impossible in the West Indies to dis- 

 tinguish between modern Haitian forms and aboriginal ceramics. 

 A study of methods of tempering practiced by different peoples is 

 of greater value because of the wide range of materials used in 

 tempering, which differ usually from area to area, as tempering with 

 shell in aboriginal Florida but with crushed rock particles in Santo 

 Domingo. 



Such objects as lime, mica, sand, ashes, bits of crushed rock or 

 rounded pebbles, and bits of broken shell are used by different Amer- 

 ican tribes, the strangest tempering material perhaps being that used 

 by the Eskimo of western Alaska, namely, seal blood and hair. It is 

 impossible to make pottery from certain durable clays that occur in 

 pure form without the use of tempering matter. This discovery was 

 made at an early time and contributed to the development of pottery. 

 In one of the oldest areas of culture development, the Mesopotamian- 

 Egyptian culture area, we find at an early date clay bricks made 

 with a tempering material of chopped straw. Chinese bricks like- 

 wise depend for durability on this addition of chopped straw to 

 relieve unequal stress which develops in the hardening of the clay 

 during firing. Without such addition all j^ottery from pure clay 

 would crack from unequal stress. The modern Mexican potter does 

 not employ a tempering material because he finds it unnecessary 

 owing to the homogeneous clays that he uses in his art. Some of the 

 aboriginal earthenware from coastal villages in eastern Santo Do- 

 mingo likewise show no extraneous tempering material due to the 

 presence of sand in large quantities in the clay. Elsewhere in Santo 

 Domingo the aboriginal potter added bits of broken steatite, pebbles, 

 potsherds, and occasionally even bits of charred wood, as a temper. 



Another interesting phase in the manufacture of ceramics having 

 value for comparative purposes is the color. Color in earthenware 

 forms is always due to the presence of iron or the form in which 

 iron occurs. If iron occurs in the form of carbonate it burns to a 

 red oxide. With silicate of iron present the earthenware burns to 

 a creamy color. These two outstanding colors of wares, that is, 

 gray ware and red ware, are the characteristic colors of unpainted 

 earthenware forms in aboriginal Santo Domingo, the clays that 

 burn to a red oxide occurring near the surface while the creamy 

 colored ware or gray ware is derived from clays obtained from a 

 depth of 3 and sometimes 6 or more feet. A characteristic form of 

 earth used in making pottery of a very porous and coarse texture 



