its shape perfectly, the substance is still clay, capable 

 of being transformed from one of these conditions 

 to another, simply by moistening or drying as the case 

 may be. But in the next step of pottery manufacture 

 the one that follows next after the molding, turn- 

 ing, and coloring processes the plastic substance, 

 clay, is changed into an altogether different substance 

 by the application of intense heat. It can be ground 

 to impalpable fineness, blunged into what appears to 

 be clay slip, and passed through the various processes 

 through which it passed in its journey through the 

 pottery works before being fired ; but it will have none 

 of the characteristic plastic qualities of the original 

 clay, nor can pottery of any kind be made from it, any 

 more than can be done with powdered granite or marble. 

 The explanation is that the heat has driven off the 

 "water of combination" as the chemist calls it, and 

 there is no known means of replacing it. This water 

 of combination, it should be understood, is a thing 

 quite apart from the water which is held in suspension 

 in the plastic clay, and which may be driven off by 

 drying. The water of combination is an integral part 

 of the molecule of clay, and remains unchanged whether 

 the clay is in a moist or dry state. No amount of man- 

 ipulating in the machinery of the pottery affects it in 

 any way until it is brought to a red heat in the biscuit 

 oven. Then it frees itself from its clay associates, 

 and no way is known of inducing it to take up its orig- 

 inal relations again. Its leaving causes the body of 

 the clay to shrink, pure clay having so much shrinkage 

 that the potter finds it necessary to counteract the ten- 



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