The contract itself is unequivocal; the District Court concluded, and it is not disputed here, that by the clear and explicit terms of the contract reservations, '(respondents') interests in the oil, gas, sulphur and other minerals terminated . . . no later than July 23, 1947, and August 30, 1949, unless Act 315 of 1940 has caused the reservations of the servitudes in favor of (respondents) to be