A bill to amend the Federal Coal Mine Health and Safety Act of 1969 to provide that, for purposes of payments under section 411 in respect of the death of any miner whose death occurred after the date of enactment of such act, there shall be an irrebuttable presumption that his death was due to pneumoconiosis or that at the time of his death he was totally disabled by pneumoconiosis, if such miner was employed for 20 years in one or more underground coal mines.