avily charred. The charring on the
front of the posts was sharply limited by the shadow of a wall. This
wall had however been completely demolished by the blast, which of
course arrived some time after the flash. At the north edge of the
Torpedo works, 1.05 miles from X, telephone poles were charred to a
depth of about 0.5 millimeters. A light piece of wood similar to the
flat side of an orange crate, was found leaning against one of the
telephone poles. Its front surface was charred the same way as the
pole, but it was evident that it had actually been ignited. The wood
was blackened through a couple of cracks and nail holes, and around the
edges onto the back surface. It seemed likely that this piece of wood
had flamed up under the flash for a few seconds before the flame was
blown out by the wind of the blast. Farther out, between 1.05 and 1.5
miles from the explosion, were many trees and poles showing a
blackening. Some of the poles had platforms near the top. The shadows
cast by the platforms were clearly visible and showed that the bomb had
detonated at a considerable height. The row of poles turned north and
crossed the mountain ridge; the flash burn was plainly visible all the
way to the top of the ridge, the farthest burn observed being at 2.0
miles from X.

Another striking effect of the flash burn was the autumnal appearance
of the bowl formed by the hills on three sides of the explosion point.
The ridges are about 1.5 miles from X. Throughout this bowl the
foliage turned yellow, although on the far side of the ridges the
countryside was quite green. This autumnal appearance of the trees
extended to about 8,000 feet from X.

However, shrubs and small plants quite near the center of explosion in
Hiroshima, although stripped of leaves, had obviously not been killed.
Many were throwing out new buds when observers visited the city.

There are two other remarkable effects of the heat radiated from the
bomb explosion. The first of these is the manner in which heat
roughened the surface of polished granite, which retained its polish
only where it was shielded from the radiated heat travelling in
straight lines from the explosion. This roughening by radiated heat
caused by the unequal expansion of the constituent crystals of the
stone; for granite crystals the melting temperature is about 600 deg
centigrade. Therefore the depth of roughening and ultimate flaking of
the granite surface indicated the