The lower court, after full trial on the issues of liability, made findings of fact and conclusions of law to the effect that liability of the United States under the Federal Tort Claims Act 1 was not proven. We affirm.

In May, June and July of 1964 the United States Air Force at Eglin A. F. Base tested an aerial spraying apparatus designed for use in defoliation operations in Viet Nam. The tests were conducted at and over (at altitudes of 150 to 1000 feet) a 2000 foot grid at the air base. They involved spraying of herbicides known as 2,4-D and 2,4,5-T in a one to one ratio.

The claimants were cotton farmers whose farms were 25 to 35 miles distant from the field. Their crops suffered injury which was asserted to be caused by the spraying operations. The testimony, mostly by experts, was extensive, and the district judge was required to make a choice as to which experts, or groups of experts, to follow. He chose to credit in *604 the main the testimony of the expert witnesses who testified for the government. This choice, under the evidence, was permissible, and his findings are not demonstrated to be “clearly erroneous”. Rule 52(a) F.R.Civ.P. The judgment below is

Affirmed.