The main goals of the physics sub-team of the academic survey team were to estimate location of the epicenter, size of the fireball, and amount of radiation, and to study the effects of radiation.
On October 7, Shigeo Hayashi visited the Koi and Takasu areas.
"When I got back to the dormitory, I heard someone say, 'There's not as much radiation as we predicted back in Tokyo.' …. The reason is still a mystery, but it could be due to the Makurazaki Typhoon."

Measuring radiation at the hypocenter

Location: Saiku-machi (now, Ote-machi 1 chome)

Team members dug a hole on the south side of Shima Hospital (the hypocenter) to measure the radiation in the soil with a Neher Cosmic Ray Telescope. The men were Yukio Miyazaki and Masao Ikeda of the Institute of Physical and Chemical Research. Using the figures obtained, they created a map showing radiation distribution.

Studying the torii gates of Hiroshima Gokoku Shrine

Location: Moto-machi
Distance from hypocenter: approx. 330m

They measured the torii knocked down by the blast before the front building of Hiroshima Gokoku Shrine. The diameter of the torii leg was more than 60 centimeters.

Radioactive substances on a roof

Location: Koi-machi (now, Koi-ue)
Distance from hypocenter: approx. 3,700m

Team members climbed on a roof in Koi-machi to collect soil and mud for samples to measure residual radiation. They looked for gutters, cracks between roof tiles, or anywhere they might find a puddle of water.

Trousers with black rain stains

Location: Koi-machi (now, Koi-ue)
Distance from hypocenter: approx 3,700m

When the team traveled to west Hiroshima to study the effects of black rain, they discovered these stained trousers in a private home in Koi-machi and learned that the rain was like dirty water.

Weather door stained with black rain

Location: Furuta-machi (now, Takasu)
Distance from hypocenter: approx. 4,200m

This weather door was part of the home of Michitaka Uda, staff member of the Hiroshima District Meteorological Observatory. The door was thrown into the yard by the blast and later soaked by black rain. The Uda family had put the door back into its frame. The team shaved off caked mud to measure the radiation level. When they discovered that the dirt was several times more radioactive than dirt at the hypocenter, the family decided to wash the door.

After Hayashi photographed a boneset plant with unusual leaf coloration in the ruins of Hiroshima Castle, he was unable to eat the sweet potato that appeared at mealtime. On the other hand, when he saw morning glories in the Saikoji Temple graveyard, he felt a refreshing calm and instinctively clicked the shutter. "That quiet moment engraved itself in my mind and still comes to me sometimes."

Boneset plant with variegated coloration

Location: Moto-machi
Distance from hypocenter: approx. 900m

This boneset plant grew in the ruins of the Imperial Headquarters at Hiroshima Castle. Radiation damage caused unusual white coloration. Setaria viridis and Cyperus microiria growing in the same area showed no such damage

Castsor-oil plant with variegated coloration

Location: Moto-machi
Distance from hypocenter: approx. 900m

This castor oil plant was picked in the area of Hiroshima Gokoku Shrine. Radiation damage caused chlorophyll deficiency and color variegation. The variegated colors are yellow or white. Some of the leaves show immature growth.

Phytolacca esculenta with unusual coloration

Location: Moto-machi
Distance from hypocenter: approx. 900m

This Phytolacca esculenta grew in the ruins of the Imperial Headquarters at Hiroshima Castle. Radiation damage caused unusual coloration and deformation of the leaves.

Morning glories in the Saikoji Temple graveyard

Location: Saiku-machi (now, Ote-machi 1 chome)
Distance from hypocenter: approx. 70m

The graveyard of Saikoji Temple at the hypocenter. Despite the rumor that "nothing will grow around the hypocenter for 75 years," eye-catching morning glories vigorously pushed up vines between the gravestones. Hayashi thought that one had bloomed several hours before the photo was taken because the flowers were almost shut.

Eucalyptus and maruba willow at Hiroshima Castle

Location: Moto-machi
Distance from hypocenter: approx. 720m

In Hiroshima Castle, this path runs from the second bailey (ninomaru) across the moat to the ruins of a gate on the central bailey (honmaru). Leaves are growing on the eucalyptus tree in the center. Behind and to the right of the tilted cedar tree is the thick trunk of a maruba willow. In 1971, a typhoon tore off the top of the eucalyptus and left a trunk 2.5 meter tall. The maruba willow's trunk hollowed out and is now supported by posts, but both trees still leaf out every year.