16 INTRODUCTION. 
been applied to it ; but, in mineralogy, this name has 
usually been given to a mixture of alum, quartz, and 
other substances. Sir H. Davy has obtained from 
alumine a metallic basis, called aluminum. 
35. Zircon, when freed from those substances with 
which it is combined, is a white and somewhat rough 
powder, insipid to the taste, insoluble in water, and 
about four times as heavy as that fluid. It is found in 
the two kinds of precious stones called jargoon and 
hyacinth, and has not hitherto been applied to any 
useful purpose. 
36. Glucine is a kind of earth of peculiar nature, 
which is found in the emerald and beryl, and, when 
purified, forms a soft and white powder, without smell, 
and of sweetish taste. To the last of these qualities it is 
indebted for its name, which is derived from a Greek 
word signifying sweet. It is somewhat unctuous to the 
touch, and about three times as heavy as water. The uses 
of this earth, whatever they may be, are not known. 
37. Yttria is an earth which, among other particulars, 
differs from glucine by its weight, as it is nearly five 
times heavier than water. In a natural state it occurs 
as the basis of a black Swedish mineral, called gadoli- 
nite. When cleansed, by chemical process, from all its 
impurities, it is a fine, white, and inodorous powder. 
38. Barytes is a white, porous, and very heavy earth, 
which can only be obtained pure by chemical process. 
It is easily reduced to powder, and is soluble in all 
kinds of acids. To the taste it is harsh and caustic ; 
and, if taken into the stomach, proves an extremely 
virulent poison. In some respects it agrees with the 
alkalies (42), particularly in its property of changing 
blue vegetable colours to green, and in corroding, like 
