the road. Various other surfaces were discolored in different ways by the
radiated heat.

As has already been mentioned the fact that radiant heat traveled only in
straight lines from the center of explosion enabled observers to determine
the direction toward the center of explosion from a number of different
points, by observing the "shadows" which were cast by intervening objects
where they shielded the otherwise exposed surface of some object. Thus the
center of explosion was located with considerable accuracy. In a number of
cases these "shadows" also gave an indication of the height of burst of the
bomb and occasionally a distinct penumbra was found which enabled observers
to calculate the diameter of the ball of fire at the instant it was
exerting the maximum charring or burning effect.

One more interesting feature connected with heat radiation was the charring
of fabric to different degrees depending upon the color of the fabric. A
number of instances were recorded in which persons wearing clothing of
various colors received burns greatly varying in degree, the degree of burn
depending upon the color of the fabric over the skin in question. For
example a shirt of alternate light and dark gray stripes, each about 1/8 of
an inch wide, had the dark stripes completely burned out but the light
stripes were undamaged; and a piece of Japanese paper exposed nearly 1 1/2
miles from X had the characters which were written in black ink neatly
burned out.



CHARACTERISTICS OF THE INJURIES TO PERSONS