The annexed figure shows the form adopted by the inventor for oil
and kerosene lamps. As may be seen, the chimney consists of two cones, A
and B, connected end to end by their small bases. The upper one, A, or
divergent cone, is constructed according to a variable angle, but one
which, in order to produce its maximum effect, ought not to differ much
from 5 deg.. This cone rests upon the convergent one, B, whose angle, as we
have said, varies between 35 deg. and 45 deg.. To the large base of this cone
there is soldered a cylindrical part, c, designed for fixing the chimney
to the holder. The height given the divergent cone is likewise variable,
but a very beautiful light is obtained, when it is equal to six times the
diameter of the contracted part. When the lamp is designed to be used in a
still atmosphere, free from abrupt currents of air, the height may be
reduced to four times the diameter of the base, without the light being
thereby rendered any the less bright. As for the height to be given the
convergent cone, B, that is determined by the opening of the angle
according to which it has been constructed. Finally, as a general thing,
the diameter of the small base should be equal to half the large base of
the convergent cone, B.
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