Possible Clues:

• With 55-Across, MgSO4.7H2O
• Town where magnesium sulfate salts were first used medicinally
• Spa town noted for its salts
• The Oaks and Derby are run here
• Coronation Cup setting
• Racecourse record some cannot complete
• Salty poems are made of this
• One downs such salts to get moving
• Site of the second leg of the English Triple Crown
• One downs these assaults to get one moving