‘ So Pottery Among Savage Races. [ February, 
flat slabs of stone which they cement together with a composi- 
tion of seal’s blood applied warm, the vessel being held at the 
same time over the flame of a lamp, which dries the plaster to the 
hardness of stone, and in a note he adds, that “the cement is 
composed of seal’s blood, of whitish clay and of dog’s hair. 
The natives think that the hair of a female dog would spoil the 
composition and prevent its sticking.” On the Lower Murray the 
natives line a hole in the ground with clay, and cook their food 
in it, and sometimes they coat wooden vessels and gourds with 
clay to prevent their being burned. Both these customs just 
described might lead to the invention of pottery. 
The material of which pottery is made is clay. Ordinary clay 
consists of fine particles of more or less decomposed feldspar, 
mixed with a larger or smaller per centage of free silica, which 
last may exist, either as an impalpable powder, or as a more or less 
coarse sand. 
Kaolinite, used in the manufacture of porcelain, is a silicate of 
alumina derived from the decomposition of feldspar, containing 
soda or potash, and it consists mainly of a mixture of silicate of 
alumina and free silica. 
Pure clay will not make pottery, because of its tendency to 
shrink and crack in drying and baking. It must, therefore, be 
mixed with some substance to counteract this tendency. In the 
making of sundried bricks, the Egyptians found it necessary to 
mix the clay with straw. 
In pottery, the substance added is called by the Finch a 
dégraissant. One of the best materials for this purpose is sand, 
or powdered silica in some form, especially if the ware is to be 
burned at a high temperature. 
The Danish archeologists have shown that the clay of which 
the pottery of the Kjoekkenmceddings was made, was mixed 
with powdered granite, apparently obtained by heating the rock 
and plunging it into water. In Chiloé to-day, the natives obtain 
a dégraissant for pottery in the same way (Wagner Chimie Indus- 
trielle. Tomi, 555) In some kinds of earthenware manufac- 
tured in England and on the Continent, powdered flint is added 
to the clay, the flints being prepared by heating them red hot, 
then throwing them into water, and afterwards pulverizing themi 
(Brogniart, Arts Cer. 1854, i, 71). 
Sometimes a cement of pulverized ae cite or terra-cotta is 
