Both the 1937 act of sale and the 1939 judgment of condemnation reserved to the respondent Little Lake Misere oil, gas, sulphur, and other minerals for a period of 10 years from the date of vesting of title in the United States.2 The reservation was to continue in effect 'as long (after the initial ten-year period) as oil, gas, sulphur or other mineral is produced . . . or so long thereafter as (r