duced elsewhere even by tlie selfsame artisans. It is to sonic extent 

 owing to these reasons that the great potteries of the world maintain 

 their distinctive styles, and also lose them as in the cases when- the 

 finest modern examples are inferior to the older work. The loss of the 

 art of the ancients, renowned for their pottery and glazes, is possibly 

 due to this cause more than to the inability of modern science and 

 industry to duplicate their cunning in artifice. For the reasons outlined 

 we find our clays with all shades of variation in their useful properties. 



PRODUCTION AND IMPORTATION OF CLAYS. 



The following figures taken from the statistics of the mineral resources 

 of the United States, compiled by the U. S. Geological Survey for the 

 year 1902, show in an interesting way the condition of our clay-producing 

 industry: Total imports of clays, 168,551 long tons, valuation $1,154,- 

 S().~> : total domestic production of clays, 1,299,426 long tons, valuation, 

 $2,061,072. 



Altogether the total amount of clays imported into this country is 

 between one-seventh and one-eighth of that produced here, while the 

 valuation of the latter is less than twice that of the former. Doubtless 

 in time the rich clay deposits of America will be developed to a point 

 where this considerable importation of expensive clays will cease, and 

 one of the factors in this progress will be a better understanding of the 

 useful qualities of clays. 



KINDS OF CLAY. 



With few exceptions residual clays, or those derived from the decom- 

 position of rocks in place, are fit only for the commoner grades of brick 

 and earthenware. Nearly all the smoother and finer textured clays are 

 formed from the sedimentary plastic products of rock decay. These 

 beds may be, however, of a widely different nature, some being sandy, 

 or to use a technical expression, " lean," and others very fine-grained, 

 plastic, and "fat." By the accumulation of beds of fine-grained 

 material, one on top of another, the clays become consolidated into 

 shales. These shales which are much used in certain localities are 

 sometimes as hard as rock, but when ground and mixed with water 

 yield a plastic, workable mass. In actual pottery practice it is usual 

 to mix several different kinds of clays, thus combining the useful qual- 

 ities of each. Probably more than 90 per cent of all manufactured 

 articles are molded of a mixture of at least three cla3 T s. 



The various sorts of clays have come to be distinguished by different 

 names ; thus one hears of stone-ware, china, and brick clays ; pipe clays, 

 ball clays; fire clays, and kaolins. These distinctions are not very exact, 

 and in most cases merely show the local use to which the clay is put. 

 China clays are usually white or burn white, and, when mixed with ball 

 clay, ground feldspar, and quartz, are used in the manufacture of por- 



