Eyewitness Report by Cyril S. Smith

INTEROFFICE MEMORANDUM, July 25, 1945

To: Lieutenant Taylor
From: C. S. Smith

“You requested me to write a brief description of the Trinity shot. Since this occurred over a week ago, my impressions have undoubtedly been considerably modified by subsequent discussion, and many features have faded from memory.

I was at the base camp, behind a five-foot embankment near the water tanks at T=0. I was facing away from the shot, bent below the bank’s top. In addition, my eyes were partly covered by a welder’s glass. For an estimated two seconds (though it may have been less), I watched the ground from the corner of my eye. Even though this was lighted by reflection from the clouds, it was intensely bright and free from color. Since the shot, there has been some discussion about the duration of this intense light. Still, I recollect that I opened and closed my eyes several times and waited for the light to decrease in intensity before turning to face the reaction zone directly. Even after the estimated 2 seconds, the light was still intense enough to be seen through the welder’s glass. Still, there was no direct ball of fire, structure, or symmetry; this part of the phenomenon sed.

The appearance of a turbulent gas undergoing combustion was quite surprising. It looked not much different from the film of the 100-ton shot or any large fire, for instance, an oil tank fire or the Graf Zeppelin. After another second, I removed the welder’s glass and looked directly. As the primary light became less intense, the bluish ionization zone became visible, extending to a diameter almost twice that of the area where there was incandescence. I noticed a dust cloud traveling near the ground, and at some stage (I am not sure whether early or late in the proceedings, but the shot illuminated it), I noticed a ring, supposedly of moisture condensed by the rarefaction wave, at a level slightly below the clouds. This ring did not spread but, once formed, seemed to remain stationary.

At the instant after the shot, my reactions were compounded of relief that “it worked,”; consciousness of extreme silence, and a momentary question as to whether we had done more than we intended. Practically none of the watchers made any vocal comment until after the shock wave had passed, and even then, the cheers were not intense or prolonged. The joy of most observers seemed to increase for 30 minutes afterward as they had a chance to absorb the significance of the achievement.

The rising of the cloud of reaction products above the cloud level seems to have proceeded rapidly but in a typical fashion. It was noticeable that there were several rough projections, indicating high local turbulence. Shortly after the smoke column with its mushroom top was formed, wind currents distorted it into a jagged or corkscrew appearance. A dust cloud was over the ground, extending for a considerable distance. A shadow, whether of dust or moisture particles, hung close to the ground and slowly drifted east into the hills, persisting for over an hour.

The apparent fact that all of the reaction products were not proceeding upward in a neat ball but were lagging and being blown by low-altitude winds over the ground in the direction of inhabited areas produced a definite reflection that this is not a pleasant weapon we have made. Later reviews were on the manner of defense against it and the realization that a city is henceforth not the place in which to live.

I repeat that no attention should be paid to any comment made in this report since the described events occurred many days ago.”

Cyril Stanley Smith

Source: U.S. National Archives, Record Group 227, OSRD-S1 Committee, Box 82, folder 6, “Trinity.” Transcription: Thank you, Gene Dannen, for transcribing this document.