There was no consistency in the long range blast damage. Observers
often thought that they had found the limit, and then 2,000 feet
farther away would find further evidence of damage.
The most impressive long range damage was the collapse of some of the
barracks sheds at Kamigo, 23,000 feet south of X in Nagasaki. It was
remarkable to see some of the buildings intact to the last details,
including the roof and even the windows, and yet next to them a similar
building collapsed to ground level.
The limiting radius for severe displacement of roof tiles in Nagasaki
was about 10,000 feet although isolated cases were found up to 16,000
feet. In Hiroshima the general limiting radius was about 8,000 feet;
however, even at a distance of 26,000 feet from X in Hiroshima, some
tiles were displaced.
At Mogi, 7 miles from X in Nagasaki, over steep hills over 600 feet
high, about 10% of the glass came out. In nearer, sequestered
localities only 4 miles from X, no damage of any kind was caused. An
interesting effect was noted at Mogi; eyewitnesses said that they
thought a raid was being made on the place; one big flash was seen,
then a loud roar, followed at several second intervals by half a dozen
other loud reports, from all directions. These successive reports were
obviously reflections from the hills surrounding Mogi.