AMBER. 161 
year formed of black lead. For this purpose the mine- 
ral is sawed into slender square pieces. These are fixed 
into grooves, of the same shape, cut in cedar, or some 
other soft wood ; another piece of wood is then glued 
upon this, and the whole is worked into a circular form. 
The finer kinds of black lead are prepared for use by 
being boiled in oil before they are cut. The coarser 
kinds, and the refuse of the sawings, are melted with 
sulphur, and then cast into coarser pencils for carpen- 
ters. These may, in general, be easily distinguished by 
their sulphureous smell. The pencils that are manu- 
factured in England are more esteemed on the Conti- 
nent than any others. 
The powder produced in the sawing of pencils is 
employed for numerous purposes. It is used for giving 
a bright gloss to cast-iron grates and stoves, and de- 
fending them from rust, and from the action of fire. It 
may also be advantageously applied to the inner surface 
of wooden screws, to packing presses, the axles of va- 
rious sorts of machines, to slides, and other wood work, 
which are subject to friction. In this respect it is far 
superior either to grease or soap. The makers of razor- 
strops occasionally employ black lead in the composi- 
tion which they spread upon leather for the sharpening 
of razors ; and, on the Continent it is sometimes used 
for blackening the hair. A coarser kind of black lead 
is used for making the vessels that are used by chemists, 
called crucibles. 
RESIN FAMILY. 
224. AMBER is a substance usually of golden yellow co- 
lour, semi-transparent , and of shining and somewhat resinous 
lustre. It is occasionally seen of yellowish zvhite colour, and 
nearly opaque. 
The origin of amber is unknown. From the ants 
and other insects which it frequently contains, there 
can be no doubt that it has once been in a fluid state : 
and some writers have thought that it is a resinous juice, 
gradually modified by the action of sulphuric acid 
