340 COLUMBIAN HISTORICAL EXPOSITION AT MADRID. 



The potter s art and all subsequent progress in the art depended on 

 the tempering of the clay. It must be observed, however, that some 

 clays are naturally tempered from conditions of deposition and a mix 

 ture of clays answers the purpose of temper. The selection of clay and 

 its preparation require great care. 



The temper is of many kinds, such as broken shell, broken rock, sand, 

 ashes, mica, lime, broken potsherds, vegetable fiber, etc. The paste of 

 unbaked clay lamps of the Eskimo of the Yukon delta is mixed with 

 hair and seal blood, making a very strong ware. The earliest unbaked 

 ware, as well as the bricks with chopped straw, of the Egyptians, Assyr 

 ians, and Chinese depended for their strength and permanency 011 the 

 temper. 



The function of degraissants and cements, according to Semper, 

 &quot;besides destroying the homogeneity of the paste, is to furnish innu 

 merable points of rest throughout the mass that reduce the fragility of 

 the ware after burning and the danger of cracking, whether through 

 change of temperature or by shock. The coarser particles serve to 

 break up and distribute the undulations by which the cracks are 

 propagated, very much as a fracture in a pane of glass may be arrested 

 by boring a hole at the extremity of the crack.&quot; l 



Fine pottery can not have a coarse degraissant. The latter lowers 

 the tenacity of the paste and interferes with the surface finish. The 

 temper of shell often causes the pottery to exfoliate, or slack, in a 

 short time. 



The Catawba Indians do not use tempers, nor as a rule do the mod 

 ern Mexican potters, where a mixture of homogenous clays answers 

 the purpose. 



Following the preparation of the clay the next step is the construc 

 tion of the vessel. 



By simple manipulation with the hands small vessels can be formed 

 from lumps of clay. Larger vessels can not be modeled, but may be 

 laid up with ropes of clay by the process of coiling, building up a short 

 section at a time, pressing the coils together, allowing to harden, and 

 continuing the process. Coiling is the greatest aid to the securing of 

 form in larger vessels, besides seeming to give a fibrous structure to 

 clay by arranging it in the lines of greatest tenacity. 



Even when the vessels are molded in baskets, nets, or over forms 

 coiling is in effect practiced, as the masses of clay added will assume 

 a cylindrical form in the hand of the potter before being pressed into 

 junction. 



The process of coiling is widespread and ancient: within historic 

 times it has been practiced at various points in this hemisphere as a 

 native art by the introduced African slaves. 



It is not strange that the need for molds had occurred to the early 

 potter and caused him to use baskets and forms, not unmindful of the 

 ornamentation so secured and preserving indelibly the styles of weaving. 



1 Semper. Der Stil, Band II, p. 122. 



