Four second-half goals secured champions-elect Hearts a sixth successive win by beating Dumbarton 4-0.Substitute Billy King's late brace followed strikes by Osman Sow and Danny Wilson as the Jambos maintained their 17-point gap over rivals Hibernian at the top of the Scottish Championship.Sam Nicholson and Sow both tested visiting goalkeeper Danny Rogers early on while Adam Eckersley and Callum Paterson blazed efforts over the crossbar.Sow forced a stunning save from Rogers just before the half-hour mark, with the keeper tipping a long-range effort onto the crossbar before recovering to deny Genero Zeefuik a tap-in.The hosts went ahead eight minutes after the break when Sow lashed in from close range after Dumbarton failed to deal with a Nicholson corner.The Sons were denied a leveller when Wilson produced a fine block to deny Andrew Graham following a corner and Wilson put the result beyond doubt 21 minutes from time when he headed in from Billy King's corner.King rounded the win off in style, first slaloming his way through a host of challenges and firing past Rogers before racing into the area to slot under the keeper.