Excise exemption for flax fabrics: duty capped at a prescribed ad valorem rate under delegated public interest power. The Central Government, exercising powers under sub section (1) of Section 5A of the Central Excises and Salt Act, 1944, exempts flax fabrics under heading No. 53.05 from so much of the excise duty as exceeds the amount calculated at the rate of ten per cent ad valorem, thereby capping the duty payable on those goods.