  In this paper we examine more deeply about the bending mechanism of
rod-shaped fireworks which burned from the free end. We derived new analytic
equations. Surprisingly, we obtained the bending patterns are similar to the
cornu spiral. With a few simple steps we proved that positions of points
throughout the fireworks are given by Fresnel integrals, C(x) and S(x), which
are generally found in phenomena of electromagnetic wave diffraction. Although
we deeply discussed bending of fireworks rods, however the proposed method is
likely to explain any phenomena in nature related to an evolving length scale
associated with some material that becomes progressively stiff or dry, such as
the growth of resin exuded from trees.
