Manta, the unbleached muslin which served to cover such openings in the frontier ranches, was tacked taut, allowing in air but only subdued light.
The muslin was bleached and blocked out air.
mnli hypothesis: The muslin was bleached and blocked out air. premise: Manta, the unbleached muslin which served to cover such openings in the frontier ranches, was tacked taut, allowing in air but only subdued light.