An experimental device designed by Livermore Laboratory was detonated over Yucca Flat at 6:30 a.m. today as the tenth in the current series of full scale nuclear test. Code named Owens, the device was fired from an altitude of 500 feet. It was suspended by a helium filled plastic balloon 67 feet in diameter.

There were 50 experiments on the sequence timer, 17 military effects projects, and a number of civil effects experiments were included on the associated technical program. Twenty-seven military aircraft participated in support, effects, and training missions.

Two hundred and ten U.S. Army observers witnessed the detonation from an on-site observation area. The group is part of the contingent of troops which have arrived from Fort Lewis, Washington for participation in the Army maneuver to be held in connection with the atomic test scheduled for August 19.

The cloud from this morning's shot rose to 35,000 feet. Because of the presence of light moisture (cloud) conditions over the test site at shot time, an extensive ice cap formed over the top of the cloud as it surged upward in the middle stages of its ascent. The mushroom cloud broke cleanly from the stem and is moving very slowly in a north northeasterly direction. The low level cloud formed by the stem, and surface dust is settling very slowly back to earth, with part of it drifting to the north. Early weather conditions tend to confirm that only traces of fallout will be recorded at distances outside the bombing and gunnery range. The blast was audible in Bishop, Calif.