conclusions which were reached after
thorough examination of the effects of the bombs dropped on Hiroshima
and Nagasaki:

1. No harmful amounts of persistent radioactivity were present after
the explosions as determined by:

A. Measurements of the intensity of radioactivity at the time of the
investigation; and

B. Failure to find any clinical evidence of persons harmed by
persistent radioactivity.

The effects of the atomic bombs on human beings were of three main
types:

A. Burns, remarkable for (1) the great ground area over which they
were inflicted and (2) the prevalence of "flash" burns caused by the
instantaneous heat radiation.

B. Mechanical injuries, also remarkable for the wide area in which
suffered.

C. Effects resulting from penetrating gamma radiation. The effects
from radiation were due to instantaneous discharge of radiation at the
moment of explosion and not to persistent radioactivity (of either
fission products or other substances whose radioactivity might have
been induced by proximity to the explosions).

The effects of the atomic bombs on structures and installations were of
two types:

A. Destruction caused by the great pressure from the blast; and

B. Destruction caused by the fires, either started directly by the
great heat radiation, or indirectly through the collapse of buildings,
wiring, etc.

4. The actual tonnage of T.N.T. which would have caused the same blast
damage was approximately of the order of 20,000 tons.

5. In respect to their height of burst, the bombs performed exactly
according to design.

6. The bombs were placed in such positions that they could not have
done more damage from any alternative bursting point in either city.

7. The heights of burst were correctly chosen having regard to the
type of destruction it was desired to cause.

8. The information collected would enable a reasonably accurate
prediction to be made of the blast damage likely to be caused in any
city where an atomic explosion could be effected.

THE SELECTION OF THE TARGET

Some of the most frequent queries concerning the atomic bombs are those
dealing with the selection of the targets and the decision as to when
the bombs would be used.

The approximate date for the first use of the bomb was set in the fall
of 1942 after the Army had taken over the direction of and
responsibility for the atomic bomb project. At that time, under the
scientific assumptions whic