u MET.D MUSEUAr OF NATURAL HISTORY 
right upon entering from Hall 07 is occupied by a clay collec- 
tion and a collection of mineral paints, the space to the left by 
clays, soils, sands and cements. 
The key to the arrangement of the clays is given by a synop- 
tic collection which occupies the entire length of two cases along 
the north wall. In this series are displayed typical specimens of 
each of the twenty-nine classes of clays of Orton’s classification. 
Their relations to each other and to the rocks from which they 
are derived are expressed b}^ a method of grouping and by a 
number of lines connecting the various groups. If these lines 
and the associated specimens be considered as a kind of genea- 
logical tree of the clays the meaning of this series will be evi- 
dent. Each specimen of clay in this series has received in order 
a class number printed upon the label in Roman numerals. As 
a similar numeral is placed upon the labels of all other clays 
shown in this hall, the nature of any clay shown may be deter- 
mined in a moment by referring to the specimen in the synoptic 
collection with the same class number. After looking over the 
synoptic collection the visitor should inspect the series illustrat- 
ing the effects upon their useful properties of the impurities 
commonly present in clays. The greater part of the space 
devoted to cla}^s is occupied by specimens arranged according to 
industrial values. These are arranged in three series, each sub- 
divided and numbered according to the synoptic collection. Each 
class of specimens is accompanied by a descriptive label. Each 
specimen is accompanied by a carefully burned briquette of the 
same clay which illustrates the color, texture, shrinkage, vitrifi- 
cation and other properties of the clay in question when burned. 
The three collections are : 
1. The red-burning clays, which are red, pink and yellow 
when burned and chiefly used for brick, tile, coarse pottery and 
other common uses. With these are placed the clays of similar 
properties which burn to a greenish yellow from the presence of 
lime. 
2. The buff-burning clays, which burn to a buff color and 
include fire clays and most potters’ clays. 
3. The white and ivory-burning clays, which burn white or 
nearly so. Here are placed the kaolins, porcelain and china 
clays, paper and pipe clays, and other comparatively valuable 
clays. 
