EARTHS. 15 
a metal united with oxygen (21). These, which have 
the same affinity with their respective bases as rust has 
to iron, are silex., lime, barytes, and alumine. Until, 
however, some further light be thrown upon their na- 
ture and constitution, they must continue to hold their 
former situation of simple earths. 
33. Silex, or Siliceous Earth, is the basis of all sub- 
stances known by the name of quartz and silex (76). 
In a state of nature it has never been found pure ; but, 
in combination with other substances, it abounds in 
almost every country of the globe. Common flint (90) 
contains ninety-seven parts in a hundred of silex : it 
consequently has given its name to this earth, silex 
being the Latin word for flint. When purified it is a 
white powder, the particles of which are harsh to the 
touch, as if they consisted of very minute grains of 
sand. Jt is not quite three times as heavy as water, 
and has neither taste nor smell. Water will not dis- 
solve it, nor any kind of acid, except fluoric. Sir H. 
Davy has discovered it to have a metallic basis, to 
which he has given the name of silicium. 
34*. Alumine is a kind of earth, so called from its 
forming the basis of alum (197). It is soft, compact, 
and tenacious ; about twice the weight of water, and, 
when breathed upon, has a smell which is peculiar to 
all clayey productions. In the fire it shrinks, and be- 
comes so hard as even to yield sparks when struck 
against steel. It readily absorbs water, and is dissolved 
by most acids. Some writers state that pure alumine 
has been discovered in a native state near Halle, in 
Germany. It is found in a crystallized form, and 
nearly in a state of purity, in the Oriental ruby and 
sapphire. The name of argil, or clay, has sometimes 
